# SQLAlchemy 0.7.1 Documentation

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Version: 0.7.1 Last Updated: 06/05/2011 13:13:59

# SQL Statements and Expressions API

This section presents the API reference for the SQL Expression Language. For a full introduction to its usage, see SQL Expression Language Tutorial.

## Functions

The expression package uses functions to construct SQL expressions. The return value of each function is an object instance which is a subclass of `ClauseElement`.

`sqlalchemy.sql.expression.``alias`(selectable, name=None)

  Return an `Alias` object.

  An `Alias` represents any `FromClause` with an alternate name assigned within SQL, typically using the `AS` clause when generated, e.g. `SELECT * FROM table AS aliasname`.

  Similar functionality is available via the `alias()` method available on all `FromClause` subclasses.

  When an `Alias` is created from a `Table` object, this has the effect of the table being rendered as `tablename AS aliasname` in a SELECT statement.

  For `select()` objects, the effect is that of creating a named subquery, i.e. `(select ...) AS aliasname`.

  The `name` parameter is optional, and provides the name to use in the rendered SQL. If blank, an “anonymous” name will be deterministically generated at compile time. Deterministic means the name is guaranteed to be unique against other constructs used in the same statement, and will also be the same name for each successive compilation of the same statement object.

  Parameters:

  - selectable – any `FromClause` subclass, such as a table, select statement, etc.
  - name – string name to be assigned as the alias. If `None`, a name will be deterministically generated at compile time.

`sqlalchemy.sql.expression.``and_`(*clauses)

  Join a list of clauses together using the `AND` operator.

  The `&` operator is also overloaded on all `_CompareMixin` subclasses to produce the same result.

`sqlalchemy.sql.expression.``asc`(column)

  Return an ascending `ORDER BY` clause element.

  e.g.:

      someselect.order_by(asc(table1.mycol))

  produces:

      ORDER BY mycol ASC

`sqlalchemy.sql.expression.``between`(ctest, cleft, cright)

  Return a `BETWEEN` predicate clause.

  Equivalent of SQL `clausetest BETWEEN clauseleft AND clauseright`.

  The `between()` method on all `_CompareMixin` subclasses provides similar functionality.

`sqlalchemy.sql.expression.``bindparam`(key, value=None, type_=None, unique=False, required=False, callable_=None)

  Create a bind parameter clause with the given key.

  Parameters:

  - key – the key for this bind param. Will be used in the generated SQL statement for dialects that use named parameters. This value may be modified when part of a compilation operation, if other `_BindParamClause` objects exist with the same key, or if its length is too long and truncation is required.
  - value – Initial value for this bind param. This value may be overridden by the dictionary of parameters sent to statement compilation/execution.
  - callable_ – A callable function that takes the place of “value”. The function will be called at statement execution time to determine the ultimate value. Used for scenarios where the actual bind value cannot be determined at the point at which the clause construct is created, but embedded bind values are still desirable.
  - type_ – A `TypeEngine` object that will be used to pre-process the value corresponding to this `_BindParamClause` at execution time.
  - unique – if True, the key name of this BindParamClause will be modified if another `_BindParamClause` of the same name already has been located within the containing `ClauseElement`.
  - required – a value is required at execution time.

`sqlalchemy.sql.expression.``case`(whens, value=None, else_=None)

  Produce a `CASE` statement.

  whens
    A sequence of pairs, or alternatively a dict, to be translated into “WHEN / THEN” clauses.
  value
    Optional for simple case statements, produces a column expression as in “CASE <expr> WHEN ...”
  else_
    Optional as well, for case defaults produces the “ELSE” portion of the “CASE” statement.

  The expressions used for THEN and ELSE, when specified as strings, will be interpreted as bound values. To specify textual SQL expressions for these, use the `literal_column()` construct.

  The expressions used for the WHEN criterion may only be literal strings when “value” is present, i.e. CASE table.somecol WHEN “x” THEN “y”. Otherwise, literal strings are not accepted in this position, and either the text(<string>) or literal(<string>) constructs must be used to interpret raw string values.

  Usage examples:

      case([(orderline.c.qty > 100, item.c.specialprice),
            (orderline.c.qty > 10, item.c.bulkprice)
          ], else_=item.c.regularprice)
      case(value=emp.c.type, whens={
              'engineer': emp.c.salary * 1.1,
              'manager':  emp.c.salary * 3,
          })

  Using `literal_column()`, to allow for databases that do not support bind parameters in the `then` clause. The type can be specified which determines the type of the `case()` construct overall:

      case([(orderline.c.qty > 100,
              literal_column("'greaterthan100'", String)),
            (orderline.c.qty > 10, literal_column("'greaterthan10'",
              String))
          ], else_=literal_column("'lethan10'", String))

`sqlalchemy.sql.expression.``cast`(clause, totype, **kwargs)

  Return a `CAST` function.

  Equivalent of SQL `CAST(clause AS totype)`.

  Use with a `TypeEngine` subclass, i.e:

      cast(table.c.unit_price * table.c.qty, Numeric(10,4))

  or:

      cast(table.c.timestamp, DATE)

`sqlalchemy.sql.expression.``column`(text, type_=None)

  Return a textual column clause, as would be in the columns clause of a `SELECT` statement.

  The object returned is an instance of `ColumnClause`, which represents the “syntactical” portion of the schema-level `Column` object. It is often used directly within `select()` constructs or with lightweight `table()` constructs.

  Note that the `column()` function is not part of the `sqlalchemy` namespace. It must be imported from the `sql` package:

      from sqlalchemy.sql import table, column

  Parameters:

  - text – the name of the column. Quoting rules will be applied to the clause like any other column name. For textual column constructs that are not to be quoted, use the `literal_column()` function.
  - type_ – an optional `TypeEngine` object which will provide result-set translation for this column.

  See `ColumnClause` for further examples.

`sqlalchemy.sql.expression.``collate`(expression, collation)

  Return the clause `expression COLLATE collation`.

  e.g.:

      collate(mycolumn, 'utf8_bin')

  produces:

      mycolumn COLLATE utf8_bin

`sqlalchemy.sql.expression.``delete`(table, whereclause=None, **kwargs)

  Return a `Delete` clause element.

  Similar functionality is available via the `delete()` method on `Table`.

  Parameters:

  - table – The table to be updated.
  - whereclause – A `ClauseElement` describing the `WHERE` condition of the `UPDATE` statement. Note that the `where()` generative method may be used instead.

`sqlalchemy.sql.expression.``desc`(column)

  Return a descending `ORDER BY` clause element.

  e.g.:

      someselect.order_by(desc(table1.mycol))

  produces:

      ORDER BY mycol DESC

`sqlalchemy.sql.expression.``distinct`(expr)

  Return a `DISTINCT` clause.

  e.g.:

      distinct(a)

  renders:

      DISTINCT a

`sqlalchemy.sql.expression.``except_`(*selects, **kwargs)

  Return an `EXCEPT` of multiple selectables.

  The returned object is an instance of `CompoundSelect`.

  *selects
    a list of `Select` instances.
  **kwargs
    available keyword arguments are the same as those of `select()`.

`sqlalchemy.sql.expression.``except_all`(*selects, **kwargs)

  Return an `EXCEPT ALL` of multiple selectables.

  The returned object is an instance of `CompoundSelect`.

  *selects
    a list of `Select` instances.
  **kwargs
    available keyword arguments are the same as those of `select()`.

`sqlalchemy.sql.expression.``exists`(*args, **kwargs)

  Return an `EXISTS` clause as applied to a `Select` object.

  Calling styles are of the following forms:

      # use on an existing select()
      s = select([table.c.col1]).where(table.c.col2==5)
      s = exists(s)

      # construct a select() at once
      exists(['*'], **select_arguments).where(criterion)

      # columns argument is optional, generates "EXISTS (SELECT *)"
      # by default.
      exists().where(table.c.col2==5)

`sqlalchemy.sql.expression.``extract`(field, expr)

  Return the clause `extract(field FROM expr)`.

`sqlalchemy.sql.expression.``false`()

  Return a `_False` object, which compiles to `false`, or the boolean equivalent for the target dialect.

`sqlalchemy.sql.expression.``func`

  Generate SQL function expressions.

  `func` is a special object instance which generates SQL functions based on name-based attributes, e.g.:

      >>> print func.count(1)
      count(:param_1)

  The element is a column-oriented SQL element like any other, and is used in that way:

      >>> print select([func.count(table.c.id)])
      SELECT count(sometable.id) FROM sometable

  Any name can be given to `func`. If the function name is unknown to SQLAlchemy, it will be rendered exactly as is. For common SQL functions which SQLAlchemy is aware of, the name may be interpreted as a generic function which will be compiled appropriately to the target database:

      >>> print func.current_timestamp()
      CURRENT_TIMESTAMP

  To call functions which are present in dot-separated packages, specify them in the same manner:

      >>> print func.stats.yield_curve(5, 10)
      stats.yield_curve(:yield_curve_1, :yield_curve_2)

  SQLAlchemy can be made aware of the return type of functions to enable type-specific lexical and result-based behavior. For example, to ensure that a string-based function returns a Unicode value and is similarly treated as a string in expressions, specify `Unicode` as the type:

      >>> print func.my_string(u'hi', type_=Unicode) + ' ' + \
      ... func.my_string(u'there', type_=Unicode)
      my_string(:my_string_1) || :my_string_2 || my_string(:my_string_3)

  The object returned by a `func` call is an instance of `Function`. This object meets the “column” interface, including comparison and labeling functions. The object can also be passed the `execute()` method of a `Connection` or `Engine`, where it will be wrapped inside of a SELECT statement first:

      print connection.execute(func.current_timestamp()).scalar()

  A function can also be “bound” to a `Engine` or `Connection` using the `bind` keyword argument, providing an execute() as well as a scalar() method:

      myfunc = func.current_timestamp(bind=some_engine)
      print myfunc.scalar()

  Functions which are interpreted as “generic” functions know how to calculate their return type automatically. For a listing of known generic functions, see Generic Functions.

`sqlalchemy.sql.expression.``insert`(table, values=None, inline=False, **kwargs)

  Return an `Insert` clause element.

  Similar functionality is available via the `insert()` method on `Table`.

  Parameters:

  - table – The table to be inserted into.
  - values – A dictionary which specifies the column specifications of the `INSERT`, and is optional. If left as None, the column specifications are determined from the bind parameters used during the compile phase of the `INSERT` statement. If the bind parameters also are None during the compile phase, then the column specifications will be generated from the full list of table columns. Note that the `values()` generative method may also be used for this.
  - prefixes – A list of modifier keywords to be inserted between INSERT and INTO. Alternatively, the `prefix_with()` generative method may be used.
  - inline – if True, SQL defaults will be compiled ‘inline’ into the statement and not pre-executed.

  If both values and compile-time bind parameters are present, the compile-time bind parameters override the information specified within values on a per-key basis.

  The keys within values can be either `Column` objects or their string identifiers. Each key may reference one of:

  - a literal data value (i.e. string, number, etc.);
  - a Column object;
  - a SELECT statement.

  If a `SELECT` statement is specified which references this `INSERT` statement’s table, the statement will be correlated against the `INSERT` statement.

`sqlalchemy.sql.expression.``intersect`(*selects, **kwargs)

  Return an `INTERSECT` of multiple selectables.

  The returned object is an instance of `CompoundSelect`.

  *selects
    a list of `Select` instances.
  **kwargs
    available keyword arguments are the same as those of `select()`.

`sqlalchemy.sql.expression.``intersect_all`(*selects, **kwargs)

  Return an `INTERSECT ALL` of multiple selectables.

  The returned object is an instance of `CompoundSelect`.

  *selects
    a list of `Select` instances.
  **kwargs
    available keyword arguments are the same as those of `select()`.

`sqlalchemy.sql.expression.``join`(left, right, onclause=None, isouter=False)

  Return a `JOIN` clause element (regular inner join).

  The returned object is an instance of `Join`.

  Similar functionality is also available via the `join()` method on any `FromClause`.

  Parameters:

  - left – The left side of the join.
  - right – The right side of the join.
  - onclause – Optional criterion for the `ON` clause, is derived from foreign key relationships established between left and right otherwise.

  To chain joins together, use the `FromClause.join()` or `FromClause.outerjoin()` methods on the resulting `Join` object.

`sqlalchemy.sql.expression.``label`(name, obj)

  Return a `_Label` object for the given `ColumnElement`.

  A label changes the name of an element in the columns clause of a `SELECT` statement, typically via the `AS` SQL keyword.

  This functionality is more conveniently available via the `label()` method on `ColumnElement`.

  name
    label name
  obj
    a `ColumnElement`.

`sqlalchemy.sql.expression.``literal`(value, type_=None)

  Return a literal clause, bound to a bind parameter.

  Literal clauses are created automatically when non- `ClauseElement` objects (such as strings, ints, dates, etc.) are used in a comparison operation with a `_CompareMixin` subclass, such as a `Column` object. Use this function to force the generation of a literal clause, which will be created as a `_BindParamClause` with a bound value.

  Parameters:

  - value – the value to be bound. Can be any Python object supported by the underlying DB-API, or is translatable via the given type argument.
  - type_ – an optional `TypeEngine` which will provide bind-parameter translation for this literal.

`sqlalchemy.sql.expression.``literal_column`(text, type_=None)

  Return a textual column expression, as would be in the columns clause of a `SELECT` statement.

  The object returned supports further expressions in the same way as any other column object, including comparison, math and string operations. The type_ parameter is important to determine proper expression behavior (such as, ‘+’ means string concatenation or numerical addition based on the type).

  Parameters:

  - text – the text of the expression; can be any SQL expression. Quoting rules will not be applied. To specify a column-name expression which should be subject to quoting rules, use the `column()` function.
  - type_ – an optional `TypeEngine` object which will provide result-set translation and additional expression semantics for this column. If left as None the type will be NullType.

`sqlalchemy.sql.expression.``not_`(clause)

  Return a negation of the given clause, i.e. `NOT(clause)`.

  The `~` operator is also overloaded on all `_CompareMixin` subclasses to produce the same result.

`sqlalchemy.sql.expression.``null`()

  Return a `_Null` object, which compiles to `NULL`.

`sqlalchemy.sql.expression.``nullsfirst`(column)

  Return a NULLS FIRST `ORDER BY` clause element.

  e.g.:

      someselect.order_by(desc(table1.mycol).nullsfirst())

  produces:

      ORDER BY mycol DESC NULLS FIRST

`sqlalchemy.sql.expression.``nullslast`(column)

  Return a NULLS LAST `ORDER BY` clause element.

  e.g.:

      someselect.order_by(desc(table1.mycol).nullslast())

  produces:

      ORDER BY mycol DESC NULLS LAST

`sqlalchemy.sql.expression.``or_`(*clauses)

  Join a list of clauses together using the `OR` operator.

  The `|` operator is also overloaded on all `_CompareMixin` subclasses to produce the same result.

`sqlalchemy.sql.expression.``outparam`(key, type_=None)

  Create an ‘OUT’ parameter for usage in functions (stored procedures), for databases which support them.

  The `outparam` can be used like a regular function parameter. The “output” value will be available from the `ResultProxy` object via its `out_parameters` attribute, which returns a dictionary containing the values.

`sqlalchemy.sql.expression.``outerjoin`(left, right, onclause=None)

  Return an `OUTER JOIN` clause element.

  The returned object is an instance of `Join`.

  Similar functionality is also available via the `outerjoin()` method on any `FromClause`.

  Parameters:

  - left – The left side of the join.
  - right – The right side of the join.
  - onclause – Optional criterion for the `ON` clause, is derived from foreign key relationships established between left and right otherwise.

  To chain joins together, use the `FromClause.join()` or `FromClause.outerjoin()` methods on the resulting `Join` object.

`sqlalchemy.sql.expression.``over`(func, partition_by=None, order_by=None)

  Produce an OVER clause against a function.

  Used against aggregate or so-called “window” functions, for database backends that support window functions.

  E.g.:

      from sqlalchemy import over
      over(func.row_number(), order_by='x')

  Would produce “ROW_NUMBER() OVER(ORDER BY x)”.

  Parameters:

  - func – a `FunctionElement` construct, typically generated by `func`.
  - partition_by – a column element or string, or a list of such, that will be used as the PARTITION BY clause of the OVER construct.
  - order_by – a column element or string, or a list of such, that will be used as the ORDER BY clause of the OVER construct.

  This function is also available from the `func` construct itself via the `FunctionElement.over()` method.

  New in 0.7.

`sqlalchemy.sql.expression.``select`(columns=None, whereclause=None, from_obj=[], **kwargs)

  Returns a `SELECT` clause element.

  Similar functionality is also available via the `select()` method on any `FromClause`.

  The returned object is an instance of `Select`.

  All arguments which accept `ClauseElement` arguments also accept string arguments, which will be converted as appropriate into either `text()` or `literal_column()` constructs.

  Parameters:

  - columns –

    A list of `ClauseElement` objects, typically `ColumnElement` objects or subclasses, which will form the columns clause of the resulting statement. For all members which are instances of `Selectable`, the individual `ColumnElement` members of the `Selectable` will be added individually to the columns clause. For example, specifying a `Table` instance will result in all the contained `Column` objects within to be added to the columns clause.

    This argument is not present on the form of `select()` available on `Table`.

  - whereclause – A `ClauseElement` expression which will be used to form the `WHERE` clause.
  - from_obj – A list of `ClauseElement` objects which will be added to the `FROM` clause of the resulting statement. Note that “from” objects are automatically located within the columns and whereclause ClauseElements. Use this parameter to explicitly specify “from” objects which are not automatically locatable. This could include `Table` objects that aren’t otherwise present, or `Join` objects whose presence will supercede that of the `Table` objects already located in the other clauses.
  - autocommit – Deprecated. Use .execution_options(autocommit=<True|False>) to set the autocommit option.
  - bind=None – an `Engine` or `Connection` instance to which the resulting `Select` object will be bound. The `Select` object will otherwise automatically bind to whatever `Connectable` instances can be located within its contained `ClauseElement` members.
  - correlate=True – indicates that this `Select` object should have its contained `FromClause` elements “correlated” to an enclosing `Select` object. This means that any `ClauseElement` instance within the “froms” collection of this `Select` which is also present in the “froms” collection of an enclosing select will not be rendered in the `FROM` clause of this select statement.
  - distinct=False –

    when `True`, applies a `DISTINCT` qualifier to the columns clause of the resulting statement.

    The boolean argument may also be a column expression or list of column expressions - this is a special calling form which is understood by the Postgresql dialect to render the `DISTINCT ON (<columns>)` syntax.

    `distinct` is also available via the `distinct()` generative method.

    Note

    The `distinct` keyword’s acceptance of a string argument for usage with MySQL is deprecated. Use the `prefixes` argument or `prefix_with()`.

  - for_update=False – when `True`, applies `FOR UPDATE` to the end of the resulting statement. Certain database dialects also support alternate values for this parameter, for example mysql supports “read” which translates to `LOCK IN SHARE MODE`, and oracle supports “nowait” which translates to `FOR UPDATE NOWAIT`.
  - group_by – a list of `ClauseElement` objects which will comprise the `GROUP BY` clause of the resulting select.
  - having – a `ClauseElement` that will comprise the `HAVING` clause of the resulting select when `GROUP BY` is used.
  - limit=None – a numerical value which usually compiles to a `LIMIT` expression in the resulting select. Databases that don’t support `LIMIT` will attempt to provide similar functionality.
  - offset=None – a numeric value which usually compiles to an `OFFSET` expression in the resulting select. Databases that don’t support `OFFSET` will attempt to provide similar functionality.
  - order_by – a scalar or list of `ClauseElement` objects which will comprise the `ORDER BY` clause of the resulting select.
  - prefixes – a list of strings or `ClauseElement` objects to include directly after the SELECT keyword in the generated statement, for dialect-specific query features. `prefixes` is also available via the `prefix_with()` generative method.
  - use_labels=False –

    when `True`, the statement will be generated using labels for each column in the columns clause, which qualify each column with its parent table’s (or aliases) name so that name conflicts between columns in different tables don’t occur. The format of the label is <tablename>_<column>. The “c” collection of the resulting `Select` object will use these names as well for targeting column members.

    use_labels is also available via the `apply_labels()` generative method.

`sqlalchemy.sql.expression.``subquery`(alias, *args, **kwargs)

  Return an `Alias` object derived from a `Select`.

  name
    alias name

  *args, **kwargs

  > all other arguments are delivered to the `select()` function.

`sqlalchemy.sql.expression.``table`(name, *columns)

  Represent a textual table clause.

  The object returned is an instance of `TableClause`, which represents the “syntactical” portion of the schema-level `Table` object. It may be used to construct lightweight table constructs.

  Note that the `table()` function is not part of the `sqlalchemy` namespace. It must be imported from the `sql` package:

      from sqlalchemy.sql import table, column

  Parameters:

  - name – Name of the table.
  - columns – A collection of `column()` constructs.

  See `TableClause` for further examples.

`sqlalchemy.sql.expression.``text`(text, bind=None, *args, **kwargs)

  Create a SQL construct that is represented by a literal string.

  E.g.:

      t = text("SELECT * FROM users")
      result = connection.execute(t)

  The advantages `text()` provides over a plain string are backend-neutral support for bind parameters, per-statement execution options, as well as bind parameter and result-column typing behavior, allowing SQLAlchemy type constructs to play a role when executing a statement that is specified literally.

  Bind parameters are specified by name, using the format `:name`. E.g.:

      t = text("SELECT * FROM users WHERE id=:user_id")
      result = connection.execute(t, user_id=12)

  To invoke SQLAlchemy typing logic for bind parameters, the `bindparams` list allows specification of `bindparam()` constructs which specify the type for a given name:

      t = text("SELECT id FROM users WHERE updated_at>:updated",
                  bindparams=[bindparam('updated', DateTime())]
              )

  Typing during result row processing is also an important concern. Result column types are specified using the `typemap` dictionary, where the keys match the names of columns. These names are taken from what the DBAPI returns as `cursor.description`:

      t = text("SELECT id, name FROM users",
              typemap={
                  'id':Integer,
                  'name':Unicode
              }
      )

  The `text()` construct is used internally for most cases when a literal string is specified for part of a larger query, such as within `select()`, `update()`, `insert()` or `delete()`. In those cases, the same bind parameter syntax is applied:

      s = select([users.c.id, users.c.name]).where("id=:user_id")
      result = connection.execute(s, user_id=12)

  Using `text()` explicitly usually implies the construction of a full, standalone statement. As such, SQLAlchemy refers to it as an `Executable` object, and it supports the `Executable.execution_options()` method. For example, a `text()` construct that should be subject to “autocommit” can be set explicitly so using the `autocommit` option:

      t = text("EXEC my_procedural_thing()").\
              execution_options(autocommit=True)

  Note that SQLAlchemy’s usual “autocommit” behavior applies to `text()` constructs - that is, statements which begin with a phrase such as `INSERT`, `UPDATE`, `DELETE`, or a variety of other phrases specific to certain backends, will be eligible for autocommit if no transaction is in progress.

  Parameters:

  - text – the text of the SQL statement to be created. use `:<param>` to specify bind parameters; they will be compiled to their engine-specific format.
  - autocommit – Deprecated. Use .execution_options(autocommit=<True|False>) to set the autocommit option.
  - bind – an optional connection or engine to be used for this text query.
  - bindparams – a list of `bindparam()` instances which can be used to define the types and/or initial values for the bind parameters within the textual statement; the keynames of the bindparams must match those within the text of the statement. The types will be used for pre-processing on bind values.
  - typemap – a dictionary mapping the names of columns represented in the columns clause of a `SELECT` statement to type objects, which will be used to perform post-processing on columns within the result set. This argument applies to any expression that returns result sets.

`sqlalchemy.sql.expression.``true`()

  Return a `_True` object, which compiles to `true`, or the boolean equivalent for the target dialect.

`sqlalchemy.sql.expression.``tuple_`(*expr)

  Return a SQL tuple.

  Main usage is to produce a composite IN construct:

      tuple_(table.c.col1, table.c.col2).in_(
          [(1, 2), (5, 12), (10, 19)]
      )

`sqlalchemy.sql.expression.``type_coerce`(expr, type_)

  Coerce the given expression into the given type, on the Python side only.

  `type_coerce()` is roughly similar to :func:.`cast`, except no “CAST” expression is rendered - the given type is only applied towards expression typing and against received result values.

  e.g.:

      from sqlalchemy.types import TypeDecorator
      import uuid

      class AsGuid(TypeDecorator):
          impl = String

          def process_bind_param(self, value, dialect):
              if value is not None:
                  return str(value)
              else:
                  return None

          def process_result_value(self, value, dialect):
              if value is not None:
                  return uuid.UUID(value)
              else:
                  return None

      conn.execute(
          select([type_coerce(mytable.c.ident, AsGuid)]).\
                  where(
                      type_coerce(mytable.c.ident, AsGuid) ==
                      uuid.uuid3(uuid.NAMESPACE_URL, 'bar')
                  )
      )

`sqlalchemy.sql.expression.``union`(*selects, **kwargs)

  Return a `UNION` of multiple selectables.

  The returned object is an instance of `CompoundSelect`.

  A similar `union()` method is available on all `FromClause` subclasses.

  *selects
    a list of `Select` instances.
  **kwargs
    available keyword arguments are the same as those of `select()`.

`sqlalchemy.sql.expression.``union_all`(*selects, **kwargs)

  Return a `UNION ALL` of multiple selectables.

  The returned object is an instance of `CompoundSelect`.

  A similar `union_all()` method is available on all `FromClause` subclasses.

  *selects
    a list of `Select` instances.
  **kwargs
    available keyword arguments are the same as those of `select()`.

`sqlalchemy.sql.expression.``update`(table, whereclause=None, values=None, inline=False, **kwargs)

  Return an `Update` clause element.

  Similar functionality is available via the `update()` method on `Table`.

  Parameters:

  - table – The table to be updated.
  - whereclause – A `ClauseElement` describing the `WHERE` condition of the `UPDATE` statement. Note that the `where()` generative method may also be used for this.
  - values – A dictionary which specifies the `SET` conditions of the `UPDATE`, and is optional. If left as None, the `SET` conditions are determined from the bind parameters used during the compile phase of the `UPDATE` statement. If the bind parameters also are None during the compile phase, then the `SET` conditions will be generated from the full list of table columns. Note that the `values()` generative method may also be used for this.
  - inline – if True, SQL defaults will be compiled ‘inline’ into the statement and not pre-executed.

  If both values and compile-time bind parameters are present, the compile-time bind parameters override the information specified within values on a per-key basis.

  The keys within values can be either `Column` objects or their string identifiers. Each key may reference one of:

  - a literal data value (i.e. string, number, etc.);
  - a Column object;
  - a SELECT statement.

  If a `SELECT` statement is specified which references this `UPDATE` statement’s table, the statement will be correlated against the `UPDATE` statement.

## Classes

class `sqlalchemy.sql.expression.``Alias`(selectable, name=None)

  Bases: `sqlalchemy.sql.expression.FromClause`

  Represents an table or selectable alias (AS).

  Represents an alias, as typically applied to any table or sub-select within a SQL statement using the `AS` keyword (or without the keyword on certain databases such as Oracle).

  This object is constructed from the `alias()` module level function as well as the `FromClause.alias()` method available on all `FromClause` subclasses.

class `sqlalchemy.sql.expression.``_BindParamClause`(key, value, type_=None, unique=False, callable_=None, isoutparam=False, required=False, _compared_to_operator=None, _compared_to_type=None)

  Bases: `sqlalchemy.sql.expression.ColumnElement`

  Represent a bind parameter.

  Public constructor is the `bindparam()` function.

  `__init__`(key, value, type_=None, unique=False, callable_=None, isoutparam=False, required=False, _compared_to_operator=None, _compared_to_type=None)

    Construct a _BindParamClause.

    Parameters:

    - key – the key for this bind param. Will be used in the generated SQL statement for dialects that use named parameters. This value may be modified when part of a compilation operation, if other `_BindParamClause` objects exist with the same key, or if its length is too long and truncation is required.
    - value – Initial value for this bind param. This value may be overridden by the dictionary of parameters sent to statement compilation/execution.
    - callable_ – A callable function that takes the place of “value”. The function will be called at statement execution time to determine the ultimate value. Used for scenarios where the actual bind value cannot be determined at the point at which the clause construct is created, but embeded bind values are still desirable.
    - type_ – A `TypeEngine` object that will be used to pre-process the value corresponding to this `_BindParamClause` at execution time.
    - unique – if True, the key name of this BindParamClause will be modified if another `_BindParamClause` of the same name already has been located within the containing `ClauseElement`.
    - required – a value is required at execution time.
    - isoutparam – if True, the parameter should be treated like a stored procedure “OUT” parameter.

  `compare`(other, **kw)

    Compare this `_BindParamClause` to the given clause.

class `sqlalchemy.sql.expression.``ClauseElement`

  Bases: `sqlalchemy.sql.visitors.Visitable`

  Base class for elements of a programmatically constructed SQL expression.

  `compare`(other, **kw)

    Compare this ClauseElement to the given ClauseElement.

    Subclasses should override the default behavior, which is a straight identity comparison.

    **kw are arguments consumed by subclass compare() methods and may be used to modify the criteria for comparison. (see `ColumnElement`)

  `compile`(bind=None, dialect=None, **kw)

    Compile this SQL expression.

    The return value is a `Compiled` object. Calling `str()` or `unicode()` on the returned value will yield a string representation of the result. The `Compiled` object also can return a dictionary of bind parameter names and values using the `params` accessor.

    Parameters:

    - bind – An `Engine` or `Connection` from which a `Compiled` will be acquired. This argument takes precedence over this `ClauseElement`‘s bound engine, if any.
    - column_keys – Used for INSERT and UPDATE statements, a list of column names which should be present in the VALUES clause of the compiled statement. If `None`, all columns from the target table object are rendered.
    - dialect – A `Dialect` instance frmo which a `Compiled` will be acquired. This argument takes precedence over the bind argument as well as this `ClauseElement`‘s bound engine, if any.
    - inline – Used for INSERT statements, for a dialect which does not support inline retrieval of newly generated primary key columns, will force the expression used to create the new primary key value to be rendered inline within the INSERT statement’s VALUES clause. This typically refers to Sequence execution but may also refer to any server-side default generation function associated with a primary key Column.

  `execute`(*multiparams, **params)

    Compile and execute this `ClauseElement`.

    Deprecated since version 0.7: Only SQL expressions which subclass `Executable` may provide the `execute()` method.

  `get_children`(**kwargs)

    Return immediate child elements of this `ClauseElement`.

    This is used for visit traversal.

    **kwargs may contain flags that change the collection that is returned, for example to return a subset of items in order to cut down on larger traversals, or to return child items from a different context (such as schema-level collections instead of clause-level).

  `params`(*optionaldict, **kwargs)

    Return a copy with `bindparam()` elments replaced.

    Returns a copy of this ClauseElement with `bindparam()` elements replaced with values taken from the given dictionary:

        >>> clause = column('x') + bindparam('foo')
        >>> print clause.compile().params
        {'foo':None}
        >>> print clause.params({'foo':7}).compile().params
        {'foo':7}

  `scalar`(*multiparams, **params)

    Compile and execute this `ClauseElement`, returning

    Deprecated since version 0.7: Only SQL expressions which subclass `Executable` may provide the `scalar()` method.

    the result’s scalar representation.

  `self_group`(against=None)

    Apply a ‘grouping’ to this `ClauseElement`.

    This method is overridden by subclasses to return a “grouping” construct, i.e. parenthesis. In particular it’s used by “binary” expressions to provide a grouping around themselves when placed into a larger expression, as well as by `select()` constructs when placed into the FROM clause of another `select()`. (Note that subqueries should be normally created using the `Select.alias()` method, as many platforms require nested SELECT statements to be named).

    As expressions are composed together, the application of `self_group()` is automatic - end-user code should never need to use this method directly. Note that SQLAlchemy’s clause constructs take operator precedence into account - so parenthesis might not be needed, for example, in an expression like `x OR (y AND z)` - AND takes precedence over OR.

    The base `self_group()` method of `ClauseElement` just returns self.

  `unique_params`(*optionaldict, **kwargs)

    Return a copy with `bindparam()` elments replaced.

    Same functionality as `params()`, except adds unique=True to affected bind parameters so that multiple statements can be used.

class `sqlalchemy.sql.expression.``ClauseList`(*clauses, **kwargs)

  Bases: `sqlalchemy.sql.expression.ClauseElement`

  Describe a list of clauses, separated by an operator.

  By default, is comma-separated, such as a column listing.

  `compare`(other, **kw)

    Compare this `ClauseList` to the given `ClauseList`, including a comparison of all the clause items.

class `sqlalchemy.sql.expression.``ColumnClause`(text, selectable=None, type_=None, is_literal=False)

  Bases: `sqlalchemy.sql.expression._Immutable`, `sqlalchemy.sql.expression.ColumnElement`

  Represents a generic column expression from any textual string.

  This includes columns associated with tables, aliases and select statements, but also any arbitrary text. May or may not be bound to an underlying `Selectable`.

  `ColumnClause` is constructed by itself typically via the `column()` function. It may be placed directly into constructs such as `select()` constructs:

      from sqlalchemy.sql import column, select

      c1, c2 = column("c1"), column("c2")
      s = select([c1, c2]).where(c1==5)

  There is also a variant on `column()` known as `literal_column()` - the difference is that in the latter case, the string value is assumed to be an exact expression, rather than a column name, so that no quoting rules or similar are applied:

      from sqlalchemy.sql import literal_column, select

      s = select([literal_column("5 + 7")])

  `ColumnClause` can also be used in a table-like fashion by combining the `column()` function with the `table()` function, to produce a “lightweight” form of table metadata:

      from sqlalchemy.sql import table, column

      user = table("user",
              column("id"),
              column("name"),
              column("description"),
      )

  The above construct can be created in an ad-hoc fashion and is not associated with any `schema.MetaData`, unlike it’s more full fledged `schema.Table` counterpart.

  Parameters:

  - text – the text of the element.
  - selectable – parent selectable.
  - type – `types.TypeEngine` object which can associate this `ColumnClause` with a type.
  - is_literal – if True, the `ColumnClause` is assumed to be an exact expression that will be delivered to the output with no quoting rules applied regardless of case sensitive settings. the `literal_column()` function is usually used to create such a `ColumnClause`.

class `sqlalchemy.sql.expression.``ColumnCollection`(*cols)

  Bases: `sqlalchemy.util._collections.OrderedProperties`

  An ordered dictionary that stores a list of ColumnElement instances.

  Overrides the `__eq__()` method to produce SQL clauses between sets of correlated columns.

  `add`(column)

    Add a column to this collection.

    The key attribute of the column will be used as the hash key for this dictionary.

  `replace`(column)

    add the given column to this collection, removing unaliased versions of this column as well as existing columns with the same key.

    > e.g.:

    >     t = Table('sometable', metadata, Column('col1', Integer))
    >     t.columns.replace(Column('col1', Integer, key='columnone'))

    > will remove the original ‘col1’ from the collection, and add the new column under the name ‘columnname’.

    Used by schema.Column to override columns during table reflection.

class `sqlalchemy.sql.expression.``ColumnElement`

  Bases: `sqlalchemy.sql.expression.ClauseElement`, `sqlalchemy.sql.expression._CompareMixin`

  Represent an element that is usable within the “column clause” portion of a `SELECT` statement.

  This includes columns associated with tables, aliases, and subqueries, expressions, function calls, SQL keywords such as `NULL`, literals, etc. `ColumnElement` is the ultimate base class for all such elements.

  `ColumnElement` supports the ability to be a proxy element, which indicates that the `ColumnElement` may be associated with a `Selectable` which was derived from another `Selectable`. An example of a “derived” `Selectable` is an `Alias` of a `Table`.

  A `ColumnElement`, by subclassing the `_CompareMixin` mixin class, provides the ability to generate new `ClauseElement` objects using Python expressions. See the `_CompareMixin` docstring for more details.

  `anon_label`

    provides a constant ‘anonymous label’ for this ColumnElement.

    This is a label() expression which will be named at compile time. The same label() is returned each time anon_label is called so that expressions can reference anon_label multiple times, producing the same label name at compile time.

    the compiler uses this function automatically at compile time for expressions that are known to be ‘unnamed’ like binary expressions and function calls.

  `compare`(other, use_proxies=False, equivalents=None, **kw)

    Compare this ColumnElement to another.

    Special arguments understood:

    Parameters:

    - use_proxies – when True, consider two columns that share a common base column as equivalent (i.e. shares_lineage())
    - equivalents – a dictionary of columns as keys mapped to sets of columns. If the given “other” column is present in this dictionary, if any of the columns in the correponding set() pass the comparison test, the result is True. This is used to expand the comparison to other columns that may be known to be equivalent to this one via foreign key or other criterion.

  `shares_lineage`(othercolumn)

    Return True if the given `ColumnElement` has a common ancestor to this `ColumnElement`.

class `sqlalchemy.sql.expression.``_CompareMixin`

  Bases: `sqlalchemy.sql.operators.ColumnOperators`

  Defines comparison and math operations for `ClauseElement` instances.

  See `ColumnOperators` and `Operators` for descriptions of all operations.

  `asc`()

    See `ColumnOperators.asc()`.

  `between`(cleft, cright)

    See `ColumnOperators.between()`.

  `collate`(collation)

    See `ColumnOperators.collate()`.

  `contains`(other, escape=None)

    See `ColumnOperators.contains()`.

  `desc`()

    See `ColumnOperators.desc()`.

  `distinct`()

    See `ColumnOperators.distinct()`.

  `endswith`(other, escape=None)

    See `ColumnOperators.endswith()`.

  `in_`(other)

    See `ColumnOperators.in_()`.

  `label`(name)

    Produce a column label, i.e. `<columnname> AS <name>`.

    This is a shortcut to the `label()` function.

    if ‘name’ is None, an anonymous label name will be generated.

  `match`(other)

    See `ColumnOperators.match()`.

  `nullsfirst`()

    See `ColumnOperators.nullsfirst()`.

  `nullslast`()

    See `ColumnOperators.nullslast()`.

  `op`(operator)

    See `ColumnOperators.op()`.

  `startswith`(other, escape=None)

    See `ColumnOperators.startswith()`.

class `sqlalchemy.sql.operators.``ColumnOperators`

  Bases: `sqlalchemy.sql.operators.Operators`

  Defines comparison and math operations.

  By default all methods call down to `Operators.operate()` or `Operators.reverse_operate()` passing in the appropriate operator function from the Python builtin `operator` module or a SQLAlchemy-specific operator function from `sqlalchemy.expression.operators`. For example the `__eq__` function:

      def __eq__(self, other):
          return self.operate(operators.eq, other)

  Where `operators.eq` is essentially:

      def eq(a, b):
          return a == b

  A SQLAlchemy construct like `ColumnElement` ultimately overrides `Operators.operate()` and others to return further `ClauseElement` constructs, so that the `==` operation above is replaced by a clause construct.

  The docstrings here will describe column-oriented behavior of each operator. For ORM-based operators on related objects and collections, see `RelationshipProperty.Comparator`.

  `__eq__`(other)

    Implement the `==` operator.

    In a column context, produces the clause `a = b`. If the target is `None`, produces `a IS NULL`.

  `__ne__`(other)

    Implement the `!=` operator.

    In a column context, produces the clause `a != b`. If the target is `None`, produces `a IS NOT NULL`.

  `__gt__`(other)

    Implement the `>` operator.

    In a column context, produces the clause `a > b`.

  `__ge__`(other)

    Implement the `>=` operator.

    In a column context, produces the clause `a >= b`.

  `__lt__`(other)

    Implement the `<` operator.

    In a column context, produces the clause `a < b`.

  `__le__`(other)

    Implement the `<=` operator.

    In a column context, produces the clause `a <= b`.

  `__neg__`()

    Implement the `-` operator.

    In a column context, produces the clause `-a`.

  `__add__`(other)

    Implement the `+` operator.

    In a column context, produces the clause `a + b` if the parent object has non-string affinity. If the parent object has a string affinity, produces the concatenation operator, `a || b` - see `concat()`.

  `__mul__`(other)

    Implement the `*` operator.

    In a column context, produces the clause `a * b`.

  `__div__`(other)

    Implement the `/` operator.

    In a column context, produces the clause `a / b`.

  `__truediv__`(other)

    Implement the `//` operator.

    In a column context, produces the clause `a / b`.

  `__sub__`(other)

    Implement the `-` operator.

    In a column context, produces the clause `a - b`.

  `__radd__`(other)

    Implement the `+` operator in reverse.

    See `__add__()`.

  `__rsub__`(other)

    Implement the `-` operator in reverse.

    See `__sub__()`.

  `__rtruediv__`(other)

    Implement the `//` operator in reverse.

    See `__truediv__()`.

  `__rdiv__`(other)

    Implement the `/` operator in reverse.

    See `__div__()`.

  `__rmul__`(other)

    Implement the `*` operator in reverse.

    See `__mul__()`.

  `__mod__`(other)

    Implement the `%` operator.

    In a column context, produces the clause `a % b`.

  `__eq__`(other)

    Implement the `==` operator.

    In a column context, produces the clause `a = b`. If the target is `None`, produces `a IS NULL`.

  `__init__`

    x.__init__(...) initializes x; see help(type(x)) for signature

  `__le__`(other)

    Implement the `<=` operator.

    In a column context, produces the clause `a <= b`.

  `__lt__`(other)

    Implement the `<` operator.

    In a column context, produces the clause `a < b`.

  `__ne__`(other)

    Implement the `!=` operator.

    In a column context, produces the clause `a != b`. If the target is `None`, produces `a IS NOT NULL`.

  `asc`()

    Produce a `asc()` clause against the parent object.

  `between`(cleft, cright)

    Produce a `between()` clause against the parent object, given the lower and upper range.

  `collate`(collation)

    Produce a `collate()` clause against the parent object, given the collation string.

  `concat`(other)

    Implement the ‘concat’ operator.

    In a column context, produces the clause `a || b`, or uses the `concat()` operator on MySQL.

  `contains`(other, **kwargs)

    Implement the ‘contains’ operator.

    In a column context, produces the clause `LIKE '%<other>%'`

  `desc`()

    Produce a `desc()` clause against the parent object.

  `distinct`()

    Produce a `distinct()` clause against the parent object.

  `endswith`(other, **kwargs)

    Implement the ‘endswith’ operator.

    In a column context, produces the clause `LIKE '%<other>'`

  `ilike`(other, escape=None)

    Implement the `ilike` operator.

    In a column context, produces the clause `a ILIKE other`.

  `in_`(other)

    Implement the `in` operator.

    In a column context, produces the clause `a IN other`. “other” may be a tuple/list of column expressions, or a `select()` construct.

  `like`(other, escape=None)

    Implement the `like` operator.

    In a column context, produces the clause `a LIKE other`.

  `match`(other, **kwargs)

    Implements the ‘match’ operator.

    In a column context, this produces a MATCH clause, i.e. `MATCH '<other>'`. The allowed contents of `other` are database backend specific.

  `nullsfirst`()

    Produce a `nullsfirst()` clause against the parent object.

  `nullslast`()

    Produce a `nullslast()` clause against the parent object.

  `op`(opstring)

    produce a generic operator function.

    e.g.:

        somecolumn.op("*")(5)

    produces:

        somecolumn * 5

    Parameters: | operator – a string which will be output as the infix operator between this `ClauseElement` and the expression passed to the generated function.

    This function can also be used to make bitwise operators explicit. For example:

        somecolumn.op('&')(0xff)

    is a bitwise AND of the value in somecolumn.

  `operate`(op, *other, **kwargs)

    Operate on an argument.

    This is the lowest level of operation, raises `NotImplementedError` by default.

    Overriding this on a subclass can allow common behavior to be applied to all operations. For example, overriding `ColumnOperators` to apply `func.lower()` to the left and right side:

        class MyComparator(ColumnOperators):
            def operate(self, op, other):
                return op(func.lower(self), func.lower(other))

    Parameters:

    - op – Operator callable.
    - *other – the ‘other’ side of the operation. Will be a single scalar for most operations.
    - **kwargs – modifiers. These may be passed by special operators such as `ColumnOperators.contains()`.

  `reverse_operate`(op, other, **kwargs)

    Reverse operate on an argument.

    Usage is the same as `operate()`.

  `startswith`(other, **kwargs)

    Implement the `startwith` operator.

    In a column context, produces the clause `LIKE '<other>%'`

  `timetuple`

    Hack, allows datetime objects to be compared on the LHS.

class `sqlalchemy.sql.expression.``CompoundSelect`(keyword, *selects, **kwargs)

  Bases: `sqlalchemy.sql.expression._SelectBase`

  Forms the basis of `UNION`, `UNION ALL`, and other SELECT-based set operations.

class `sqlalchemy.sql.expression.``Delete`(table, whereclause, bind=None, returning=None, **kwargs)

  Bases: `sqlalchemy.sql.expression.UpdateBase`

  Represent a DELETE construct.

  The `Delete` object is created using the `delete()` function.

  `where`(whereclause)

    Add the given WHERE clause to a newly returned delete construct.

class `sqlalchemy.sql.expression.``Executable`

  Bases: `sqlalchemy.sql.expression._Generative`

  Mark a ClauseElement as supporting execution.

  `Executable` is a superclass for all “statement” types of objects, including `select()`, `delete()`, `update()`, `insert()`, `text()`.

  `bind`

    Returns the `Engine` or `Connection` to which this `Executable` is bound, or None if none found.

    This is a traversal which checks locally, then checks among the “from” clauses of associated objects until a bound engine or connection is found.

  `execute`(*multiparams, **params)

    Compile and execute this `Executable`.

  `execution_options`(**kw)

    Set non-SQL options for the statement which take effect during execution.

    Execution options can be set on a per-statement or per `Connection` basis. Additionally, the `Engine` and ORM `Query` objects provide access to execution options which they in turn configure upon connections.

    The `execution_options()` method is generative. A new instance of this statement is returned that contains the options:

        statement = select([table.c.x, table.c.y])
        statement = statement.execution_options(autocommit=True)

    Note that only a subset of possible execution options can be applied to a statement - these include “autocommit” and “stream_results”, but not “isolation_level” or “compiled_cache”. See `Connection.execution_options()` for a full list of possible options.

    See also:

    > `Connection.execution_options()`

    > `Query.execution_options()`

  `scalar`(*multiparams, **params)

    Compile and execute this `Executable`, returning the result’s scalar representation.

class `sqlalchemy.sql.expression.``FunctionElement`(*clauses, **kwargs)

  Bases: `sqlalchemy.sql.expression.Executable`, `sqlalchemy.sql.expression.ColumnElement`, `sqlalchemy.sql.expression.FromClause`

  Base for SQL function-oriented constructs.

  `__init__`(*clauses, **kwargs)

    Construct a `FunctionElement`.

  `clauses`

    Return the underlying `ClauseList` which contains the arguments for this `FunctionElement`.

  `columns`

    Fulfill the ‘columns’ contrct of `ColumnElement`.

    Returns a single-element list consisting of this object.

  `execute`()

    Execute this `FunctionElement` against an embedded ‘bind’.

    This first calls `select()` to produce a SELECT construct.

    Note that `FunctionElement` can be passed to the `Connectable.execute()` method of `Connection` or `Engine`.

  `over`(partition_by=None, order_by=None)

    Produce an OVER clause against this function.

    Used against aggregate or so-called “window” functions, for database backends that support window functions.

    The expression:

        func.row_number().over(order_by='x')

    is shorthand for:

        from sqlalchemy import over
        over(func.row_number(), order_by='x')

    See `over()` for a full description.

    New in 0.7.

  `scalar`()

    Execute this `FunctionElement` against an embedded ‘bind’ and return a scalar value.

    This first calls `select()` to produce a SELECT construct.

    Note that `FunctionElement` can be passed to the `Connectable.scalar()` method of `Connection` or `Engine`.

  `select`()

    Produce a `select()` construct against this `FunctionElement`.

    This is shorthand for:

        s = select([function_element])

class `sqlalchemy.sql.expression.``Function`(name, *clauses, **kw)

  Bases: `sqlalchemy.sql.expression.FunctionElement`

  Describe a named SQL function.

  See the superclass `FunctionElement` for a description of public methods.

  `__init__`(name, *clauses, **kw)

    Construct a `Function`.

    The `func` construct is normally used to construct new `Function` instances.

class `sqlalchemy.sql.expression.``FromClause`

  Bases: `sqlalchemy.sql.expression.Selectable`

  Represent an element that can be used within the `FROM` clause of a `SELECT` statement.

  `alias`(name=None)

    return an alias of this `FromClause`.

    This is shorthand for calling:

        from sqlalchemy import alias
        a = alias(self, name=name)

    See `alias()` for details.

  `c`

    attrgetter(attr, ...) –> attrgetter object

    Return a callable object that fetches the given attribute(s) from its operand. After, f=attrgetter(‘name’), the call f(r) returns r.name. After, g=attrgetter(‘name’, ‘date’), the call g(r) returns (r.name, r.date). After, h=attrgetter(‘name.first’, ‘name.last’), the call h(r) returns (r.name.first, r.name.last).

  `columns`

    Return the collection of Column objects contained by this FromClause.

  `correspond_on_equivalents`(column, equivalents)

    Return corresponding_column for the given column, or if None search for a match in the given dictionary.

  `corresponding_column`(column, require_embedded=False)

    Given a `ColumnElement`, return the exported `ColumnElement` object from this `Selectable` which corresponds to that original `Column` via a common anscestor column.

    Parameters:

    - column – the target `ColumnElement` to be matched
    - require_embedded – only return corresponding columns for

    the given `ColumnElement`, if the given `ColumnElement` is actually present within a sub-element of this `FromClause`. Normally the column will match if it merely shares a common anscestor with one of the exported columns of this `FromClause`.

  `count`(whereclause=None, **params)

    return a SELECT COUNT generated against this `FromClause`.

  `description`

    a brief description of this FromClause.

    Used primarily for error message formatting.

  `foreign_keys`

    Return the collection of ForeignKey objects which this FromClause references.

  `is_derived_from`(fromclause)

    Return True if this FromClause is ‘derived’ from the given FromClause.

    An example would be an Alias of a Table is derived from that Table.

  `join`(right, onclause=None, isouter=False)

    return a join of this `FromClause` against another `FromClause`.

  `outerjoin`(right, onclause=None)

    return an outer join of this `FromClause` against another `FromClause`.

  `primary_key`

    Return the collection of Column objects which comprise the primary key of this FromClause.

  `replace_selectable`(old, alias)

    replace all occurrences of FromClause ‘old’ with the given Alias object, returning a copy of this `FromClause`.

  `select`(whereclause=None, **params)

    return a SELECT of this `FromClause`.

class `sqlalchemy.sql.expression.``Insert`(table, values=None, inline=False, bind=None, prefixes=None, returning=None, **kwargs)

  Bases: `sqlalchemy.sql.expression.ValuesBase`

  Represent an INSERT construct.

  The `Insert` object is created using the `insert()` function.

  `prefix_with`(clause)

    Add a word or expression between INSERT and INTO. Generative.

    If multiple prefixes are supplied, they will be separated with spaces.

  `values`(*args, **kwargs)

    specify the VALUES clause for an INSERT statement, or the SET clause for an UPDATE.

    > **kwargs
    >   key=<somevalue> arguments
    > *args
    >   A single dictionary can be sent as the first positional argument. This allows non-string based keys, such as Column objects, to be used.

  `returning`(*cols)

    Add a RETURNING or equivalent clause to this statement.

    The given list of columns represent columns within the table that is the target of the INSERT, UPDATE, or DELETE. Each element can be any column expression. `Table` objects will be expanded into their individual columns.

    Upon compilation, a RETURNING clause, or database equivalent, will be rendered within the statement. For INSERT and UPDATE, the values are the newly inserted/updated values. For DELETE, the values are those of the rows which were deleted.

    Upon execution, the values of the columns to be returned are made available via the result set and can be iterated using `fetchone()` and similar. For DBAPIs which do not natively support returning values (i.e. cx_oracle), SQLAlchemy will approximate this behavior at the result level so that a reasonable amount of behavioral neutrality is provided.

    Note that not all databases/DBAPIs support RETURNING. For those backends with no support, an exception is raised upon compilation and/or execution. For those who do support it, the functionality across backends varies greatly, including restrictions on executemany() and other statements which return multiple rows. Please read the documentation notes for the database in use in order to determine the availability of RETURNING.

class `sqlalchemy.sql.expression.``Join`(left, right, onclause=None, isouter=False)

  Bases: `sqlalchemy.sql.expression.FromClause`

  represent a `JOIN` construct between two `FromClause` elements.

  The public constructor function for `Join` is the module-level `join()` function, as well as the `join()` method available off all `FromClause` subclasses.

  `__init__`(left, right, onclause=None, isouter=False)

    Construct a new `Join`.

    The usual entrypoint here is the `join()` function or the `FromClause.join()` method of any `FromClause` object.

  `alias`(name=None)

    return an alias of this `Join`.

    Used against a `Join` object, `alias()` calls the `select()` method first so that a subquery against a `select()` construct is generated. the `select()` construct also has the `correlate` flag set to `False` and will not auto-correlate inside an enclosing `select()` construct.

    The equivalent long-hand form, given a `Join` object `j`, is:

        from sqlalchemy import select, alias
        j = alias(
            select([j.left, j.right]).\
                select_from(j).\
                with_labels(True).\
                correlate(False),
            name=name
        )

    See `alias()` for further details on aliases.

  `select`(whereclause=None, fold_equivalents=False, **kwargs)

    Create a `Select` from this `Join`.

    The equivalent long-hand form, given a `Join` object `j`, is:

        from sqlalchemy import select
        j = select([j.left, j.right], **kw).\
                    where(whereclause).\
                    select_from(j)

    Parameters:

    - whereclause – the WHERE criterion that will be sent to the `select()` function
    - fold_equivalents – based on the join criterion of this `Join`, do not include repeat column names in the column list of the resulting select, for columns that are calculated to be “equivalent” based on the join criterion of this `Join`. This will recursively apply to any joins directly nested by this one as well.
    - **kwargs – all other kwargs are sent to the underlying `select()` function.

class `sqlalchemy.sql.expression.``Operators`

  Base of comparison and logical operators.

  Implements base methods `operate()` and `reverse_operate()`, as well as `__and__()`, `__or__()`, `__invert__()`.

  Usually is used via its most common subclass `ColumnOperators`.

  `__and__`(other)

    Implement the `&` operator.

    When used with SQL expressions, results in an AND operation, equivalent to `and_()`, that is:

        a & b

    is equivalent to:

        from sqlalchemy import and_
        and_(a, b)

    Care should be taken when using `&` regarding operator precedence; the `&` operator has the highest precedence. The operands should be enclosed in parenthesis if they contain further sub expressions:

        (a == 2) & (b == 4)

  `__or__`(other)

    Implement the `|` operator.

    When used with SQL expressions, results in an OR operation, equivalent to `or_()`, that is:

        a | b

    is equivalent to:

        from sqlalchemy import or_
        or_(a, b)

    Care should be taken when using `|` regarding operator precedence; the `|` operator has the highest precedence. The operands should be enclosed in parenthesis if they contain further sub expressions:

        (a == 2) | (b == 4)

  `__invert__`()

    Implement the `~` operator.

    When used with SQL expressions, results in a NOT operation, equivalent to `not_()`, that is:

        ~a

    is equivalent to:

        from sqlalchemy import not_
        not_(a)

  `op`(opstring)

    produce a generic operator function.

    e.g.:

        somecolumn.op("*")(5)

    produces:

        somecolumn * 5

    Parameters: | operator – a string which will be output as the infix operator between this `ClauseElement` and the expression passed to the generated function.

    This function can also be used to make bitwise operators explicit. For example:

        somecolumn.op('&')(0xff)

    is a bitwise AND of the value in somecolumn.

  `operate`(op, *other, **kwargs)

    Operate on an argument.

    This is the lowest level of operation, raises `NotImplementedError` by default.

    Overriding this on a subclass can allow common behavior to be applied to all operations. For example, overriding `ColumnOperators` to apply `func.lower()` to the left and right side:

        class MyComparator(ColumnOperators):
            def operate(self, op, other):
                return op(func.lower(self), func.lower(other))

    Parameters:

    - op – Operator callable.
    - *other – the ‘other’ side of the operation. Will be a single scalar for most operations.
    - **kwargs – modifiers. These may be passed by special operators such as `ColumnOperators.contains()`.

  `reverse_operate`(op, other, **kwargs)

    Reverse operate on an argument.

    Usage is the same as `operate()`.

class `sqlalchemy.sql.expression.``Select`(columns, whereclause=None, from_obj=None, distinct=False, having=None, correlate=True, prefixes=None, **kwargs)

  Bases: `sqlalchemy.sql.expression._SelectBase`

  Represents a `SELECT` statement.

  Select statements support appendable clauses, as well as the ability to execute themselves and return a result set.

  `__init__`(columns, whereclause=None, from_obj=None, distinct=False, having=None, correlate=True, prefixes=None, **kwargs)

    Construct a Select object.

    The public constructor for Select is the `select()` function; see that function for argument descriptions.

    Additional generative and mutator methods are available on the `_SelectBase` superclass.

  `append_column`(column)

    append the given column expression to the columns clause of this select() construct.

  `append_correlation`(fromclause)

    append the given correlation expression to this select() construct.

  `append_from`(fromclause)

    append the given FromClause expression to this select() construct’s FROM clause.

  `append_having`(having)

    append the given expression to this select() construct’s HAVING criterion.

    The expression will be joined to existing HAVING criterion via AND.

  `append_prefix`(clause)

    append the given columns clause prefix expression to this select() construct.

  `append_whereclause`(whereclause)

    append the given expression to this select() construct’s WHERE criterion.

    The expression will be joined to existing WHERE criterion via AND.

  `column`(column)

    return a new select() construct with the given column expression added to its columns clause.

  `correlate`(*fromclauses)

    return a new select() construct which will correlate the given FROM clauses to that of an enclosing select(), if a match is found.

    By “match”, the given fromclause must be present in this select’s list of FROM objects and also present in an enclosing select’s list of FROM objects.

    Calling this method turns off the select’s default behavior of “auto-correlation”. Normally, select() auto-correlates all of its FROM clauses to those of an embedded select when compiled.

    If the fromclause is None, correlation is disabled for the returned select().

  `distinct`(*expr)

    Return a new select() construct which will apply DISTINCT to its columns clause.

    Parameters: | *expr – optional column expressions. When present, the Postgresql dialect will render a `DISTINCT ON (<expressions>>)` construct.

  `except_`(other, **kwargs)

    return a SQL EXCEPT of this select() construct against the given selectable.

  `except_all`(other, **kwargs)

    return a SQL EXCEPT ALL of this select() construct against the given selectable.

  `froms`

    Return the displayed list of FromClause elements.

  `get_children`(column_collections=True, **kwargs)

    return child elements as per the ClauseElement specification.

  `having`(having)

    return a new select() construct with the given expression added to its HAVING clause, joined to the existing clause via AND, if any.

  `inner_columns`

    an iterator of all ColumnElement expressions which would be rendered into the columns clause of the resulting SELECT statement.

  `intersect`(other, **kwargs)

    return a SQL INTERSECT of this select() construct against the given selectable.

  `intersect_all`(other, **kwargs)

    return a SQL INTERSECT ALL of this select() construct against the given selectable.

  `locate_all_froms`

    return a Set of all FromClause elements referenced by this Select.

    This set is a superset of that returned by the `froms` property, which is specifically for those FromClause elements that would actually be rendered.

  `prefix_with`(*expr)

    return a new select() construct which will apply the given expressions, typically strings, to the start of its columns clause, not using any commas. In particular is useful for MySQL keywords.

    e.g.:

        select(['a', 'b']).prefix_with('HIGH_PRIORITY',
                               'SQL_SMALL_RESULT',
                               'ALL')

    Would render:

        SELECT HIGH_PRIORITY SQL_SMALL_RESULT ALL a, b

  `select_from`(fromclause)

    return a new select() construct with the given FROM expression applied to its list of FROM objects.

  `self_group`(against=None)

    return a ‘grouping’ construct as per the ClauseElement specification.

    > This produces an element that can be embedded in an expression. Note

    that this method is called automatically as needed when constructing expressions.

  `union`(other, **kwargs)

    return a SQL UNION of this select() construct against the given selectable.

  `union_all`(other, **kwargs)

    return a SQL UNION ALL of this select() construct against the given selectable.

  `where`(whereclause)

    return a new select() construct with the given expression added to its WHERE clause, joined to the existing clause via AND, if any.

  `with_hint`(selectable, text, dialect_name='*')

    Add an indexing hint for the given selectable to this `Select`.

    The text of the hint is rendered in the appropriate location for the database backend in use, relative to the given `Table` or `Alias` passed as the selectable argument. The dialect implementation typically uses Python string substitution syntax with the token `%(name)s` to render the name of the table or alias. E.g. when using Oracle, the following:

        select([mytable]).\
            with_hint(mytable, "+ index(%(name)s ix_mytable)")

    Would render SQL as:

        select /*+ index(mytable ix_mytable) */ ... from mytable

    The `dialect_name` option will limit the rendering of a particular hint to a particular backend. Such as, to add hints for both Oracle and Sybase simultaneously:

        select([mytable]).\
            with_hint(mytable, "+ index(%(name)s ix_mytable)", 'oracle').\
            with_hint(mytable, "WITH INDEX ix_mytable", 'sybase')

  `with_only_columns`(columns)

    return a new select() construct with its columns clause replaced with the given columns.

class `sqlalchemy.sql.expression.``Selectable`

  Bases: `sqlalchemy.sql.expression.ClauseElement`

  mark a class as being selectable

class `sqlalchemy.sql.expression.``_SelectBase`(use_labels=False, for_update=False, limit=None, offset=None, order_by=None, group_by=None, bind=None, autocommit=None)

  Bases: `sqlalchemy.sql.expression.Executable`, `sqlalchemy.sql.expression.FromClause`

  Base class for `Select` and `CompoundSelects`.

  `append_group_by`(*clauses)

    Append the given GROUP BY criterion applied to this selectable.

    The criterion will be appended to any pre-existing GROUP BY criterion.

  `append_order_by`(*clauses)

    Append the given ORDER BY criterion applied to this selectable.

    The criterion will be appended to any pre-existing ORDER BY criterion.

  `apply_labels`()

    return a new selectable with the ‘use_labels’ flag set to True.

    This will result in column expressions being generated using labels against their table name, such as “SELECT somecolumn AS tablename_somecolumn”. This allows selectables which contain multiple FROM clauses to produce a unique set of column names regardless of name conflicts among the individual FROM clauses.

  `as_scalar`()

    return a ‘scalar’ representation of this selectable, which can be used as a column expression.

    Typically, a select statement which has only one column in its columns clause is eligible to be used as a scalar expression.

    The returned object is an instance of `_ScalarSelect`.

  `autocommit`()

    return a new selectable with the ‘autocommit’ flag set to

    Deprecated since version 0.6: `autocommit()` is deprecated. Use `Executable.execution_options()` with the ‘autocommit’ flag.

    True.

  `group_by`(*clauses)

    return a new selectable with the given list of GROUP BY criterion applied.

    The criterion will be appended to any pre-existing GROUP BY criterion.

  `label`(name)

    return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.

    See also `as_scalar()`.

  `limit`(limit)

    return a new selectable with the given LIMIT criterion applied.

  `offset`(offset)

    return a new selectable with the given OFFSET criterion applied.

  `order_by`(*clauses)

    return a new selectable with the given list of ORDER BY criterion applied.

    The criterion will be appended to any pre-existing ORDER BY criterion.

class `sqlalchemy.sql.expression.``TableClause`(name, *columns)

  Bases: `sqlalchemy.sql.expression._Immutable`, `sqlalchemy.sql.expression.FromClause`

  Represents a minimal “table” construct.

  The constructor for `TableClause` is the `table()` function. This produces a lightweight table object that has only a name and a collection of columns, which are typically produced by the `column()` function:

      from sqlalchemy.sql import table, column

      user = table("user",
              column("id"),
              column("name"),
              column("description"),
      )

  The `TableClause` construct serves as the base for the more commonly used `Table` object, providing the usual set of `FromClause` services including the `.c.` collection and statement generation methods.

  It does not provide all the additional schema-level services of `Table`, including constraints, references to other tables, or support for `MetaData`-level services. It’s useful on its own as an ad-hoc construct used to generate quick SQL statements when a more fully fledged `Table` is not on hand.

  `count`(whereclause=None, **params)

    return a SELECT COUNT generated against this `TableClause`.

  `delete`(whereclause=None, **kwargs)

    Generate a `delete()` construct.

  `insert`(values=None, inline=False, **kwargs)

    Generate an `insert()` construct.

  `update`(whereclause=None, values=None, inline=False, **kwargs)

    Generate an `update()` construct.

class `sqlalchemy.sql.expression.``Update`(table, whereclause, values=None, inline=False, bind=None, returning=None, **kwargs)

  Bases: `sqlalchemy.sql.expression.ValuesBase`

  Represent an Update construct.

  The `Update` object is created using the `update()` function.

  `where`(whereclause)

    return a new update() construct with the given expression added to its WHERE clause, joined to the existing clause via AND, if any.

  `values`(*args, **kwargs)

    specify the VALUES clause for an INSERT statement, or the SET clause for an UPDATE.

    > **kwargs
    >   key=<somevalue> arguments
    > *args
    >   A single dictionary can be sent as the first positional argument. This allows non-string based keys, such as Column objects, to be used.

class `sqlalchemy.sql.expression.``ValuesBase`(table, values)

  Bases: `sqlalchemy.sql.expression.UpdateBase`

  Supplies support for `ValuesBase.values()` to INSERT and UPDATE constructs.

  `values`(*args, **kwargs)

    specify the VALUES clause for an INSERT statement, or the SET clause for an UPDATE.

    > **kwargs
    >   key=<somevalue> arguments
    > *args
    >   A single dictionary can be sent as the first positional argument. This allows non-string based keys, such as Column objects, to be used.

## Generic Functions

SQL functions which are known to SQLAlchemy with regards to database-specific rendering, return types and argument behavior. Generic functions are invoked like all SQL functions, using the `func` attribute:

    select([func.count()]).select_from(sometable)

Note that any name not known to `func` generates the function name as is - there is no restriction on what SQL functions can be called, known or unknown to SQLAlchemy, built-in or user defined. The section here only describes those functions where SQLAlchemy already knows what argument and return types are in use.

class `sqlalchemy.sql.functions.``AnsiFunction`(**kwargs)

  Bases: `sqlalchemy.sql.functions.GenericFunction`

class `sqlalchemy.sql.functions.``GenericFunction`(type_=None, args=(), **kwargs)

  Bases: `sqlalchemy.sql.expression.Function`

class `sqlalchemy.sql.functions.``ReturnTypeFromArgs`(*args, **kwargs)

  Bases: `sqlalchemy.sql.functions.GenericFunction`

  Define a function whose return type is the same as its arguments.

class `sqlalchemy.sql.functions.``char_length`(arg, **kwargs)

  Bases: `sqlalchemy.sql.functions.GenericFunction`

class `sqlalchemy.sql.functions.``coalesce`(*args, **kwargs)

  Bases: `sqlalchemy.sql.functions.ReturnTypeFromArgs`

class `sqlalchemy.sql.functions.``concat`(*args, **kwargs)

  Bases: `sqlalchemy.sql.functions.GenericFunction`

class `sqlalchemy.sql.functions.``count`(expression=None, **kwargs)

  Bases: `sqlalchemy.sql.functions.GenericFunction`

  The ANSI COUNT aggregate function. With no arguments, emits COUNT *.

class `sqlalchemy.sql.functions.``current_date`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`

class `sqlalchemy.sql.functions.``current_time`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`

class `sqlalchemy.sql.functions.``current_timestamp`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`

class `sqlalchemy.sql.functions.``current_user`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`

class `sqlalchemy.sql.functions.``localtime`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`

class `sqlalchemy.sql.functions.``localtimestamp`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`

class `sqlalchemy.sql.functions.``max`(*args, **kwargs)

  Bases: `sqlalchemy.sql.functions.ReturnTypeFromArgs`

class `sqlalchemy.sql.functions.``min`(*args, **kwargs)

  Bases: `sqlalchemy.sql.functions.ReturnTypeFromArgs`

class `sqlalchemy.sql.functions.``next_value`(seq, **kw)

  Bases: `sqlalchemy.sql.expression.Function`

  Represent the ‘next value’, given a `Sequence` as it’s single argument.

  Compiles into the appropriate function on each backend, or will raise NotImplementedError if used on a backend that does not provide support for sequences.

class `sqlalchemy.sql.functions.``now`(type_=None, args=(), **kwargs)

  Bases: `sqlalchemy.sql.functions.GenericFunction`

class `sqlalchemy.sql.functions.``random`(*args, **kwargs)

  Bases: `sqlalchemy.sql.functions.GenericFunction`

class `sqlalchemy.sql.functions.``session_user`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`

class `sqlalchemy.sql.functions.``sum`(*args, **kwargs)

  Bases: `sqlalchemy.sql.functions.ReturnTypeFromArgs`

class `sqlalchemy.sql.functions.``sysdate`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`

class `sqlalchemy.sql.functions.``user`(**kwargs)

  Bases: `sqlalchemy.sql.functions.AnsiFunction`