# SQLAlchemy 0.6.0 Documentation

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Version: 0.6.0 Last Updated: 04/18/2010 19:16:18

# SQL Statements and Expressions

## 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, alias=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.

  > selectable
  >   any `FromClause` subclass, such as a table, select statement, etc..
  > alias
  >   string name to be assigned as the alias. If `None`, a random name will be generated.

`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.:

      order_by = [asc(table1.mycol)]

`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)

  Create a bind parameter clause with the given key.

  value
    a default value for this bind parameter. a bindparam with a value is called a `value-based bindparam`.
  type_
    a sqlalchemy.types.TypeEngine object indicating the type of this bind param, will invoke type-specific bind parameter processing
  unique
    if True, bind params sharing the same name will have their underlying `key` modified to a uniquely generated name. mostly useful with value-based bind params.
  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(<string>) or text(<string>) 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.

  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.

`sqlalchemy.sql.expression.``collate`(expression, collation)
  Return the clause `expression COLLATE collation`.

`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.:

      order_by = [desc(table1.mycol)]

`sqlalchemy.sql.expression.``distinct`(expr)
  Return a `DISTINCT` clause.

`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.``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)

  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)

  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`.

  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 `join()` or `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).

  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` in a sql statement.

`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`.

  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 `join()` or `outerjoin()` methods on the resulting `Join` object.

`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.

  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.
  **kwargs

    Additional parameters include:

    autocommit
      Deprecated. Use .execution_options(autocommit=<True|False>) to set the autocommit option.
    prefixes
      a list of strings or `ClauseElement` objects to include directly after the SELECT keyword in the generated statement, for dialect-specific query features.
    distinct=False
      when `True`, applies a `DISTINCT` qualifier to the columns clause of the resulting statement.
    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.
    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`.
    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.
    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.
    order_by
      a scalar or list of `ClauseElement` objects which will comprise the `ORDER BY` clause of the resulting select.
    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.
    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.

`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)

  Return a `TableClause` object.

  This is a primitive version of the `Table` object, which is a subclass of this object.

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

  Create literal text to be inserted into a query.

  When constructing a query from a `select()`, `update()`, `insert()` or `delete()`, using plain strings for argument values will usually result in text objects being created automatically. Use this function when creating textual clauses outside of other `ClauseElement` objects, or optionally wherever plain text is to be used.

  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.
  bind
    an optional connection or engine to be used for this text query.
  autocommit=True
    Deprecated. Use .execution_options(autocommit=<True|False>) to set the autocommit option.
  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 `SELECT` clause of the textual statement to type objects, which will be used to perform post-processing on columns within the result set (for textual statements that produce result sets).

`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.``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, alias=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 `alias()` method available on all `FromClause` subclasses.

  `__init__`(selectable, alias=None)

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

    Construct a _BindParamClause.

    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.
    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.

  `bind`
    Returns the Engine or Connection to which this ClauseElement is bound, or None if none found.
  `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`.
  `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 the result’s scalar representation.
  `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.``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 usually created publically via the `column()` function or the `literal_column()` function.

  text
    the text of the element.
  selectable
    parent selectable.
  type
    `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`.
  `__init__`(text, selectable=None, type_=None, is_literal=False)

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

  Bases: `sqlalchemy.util.OrderedProperties`

  An ordered dictionary that stores a list of ColumnElement instances.

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

  `__init__`(*cols)
  `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.

  `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.expression.ColumnOperators`

  Defines comparison and math operations for `ClauseElement` instances.

  `asc`()
    Produce a ASC clause, i.e. `<columnname> ASC`
  `between`(cleft, cright)
    Produce a BETWEEN clause, i.e. `<column> BETWEEN <cleft> AND <cright>`
  `collate`(collation)
    Produce a COLLATE clause, i.e. `<column> COLLATE utf8_bin`
  `contains`(other, escape=None)
    Produce the clause `LIKE '%<other>%'`
  `desc`()
    Produce a DESC clause, i.e. `<columnname> DESC`
  `distinct`()
    Produce a DISTINCT clause, i.e. `DISTINCT <columnname>`
  `endswith`(other, escape=None)
    Produce the clause `LIKE '%<other>'`
  `in_`(other)
  `label`(name)

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

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

  `match`(other)

    Produce a MATCH clause, i.e. `MATCH '<other>'`

    The allowed contents of `other` are database backend specific.

  `op`(operator)

    produce a generic operator function.

    e.g.:

        somecolumn.op("*")(5)

    produces:

        somecolumn * 5

    Parameter: | 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)
  `reverse_operate`(op, other, **kwargs)
  `startswith`(other, escape=None)
    Produce the clause `LIKE '<other>%'`

class `sqlalchemy.sql.expression.``ColumnOperators`

  Defines comparison and math operations.

  `__init__`
    x.__init__(...) initializes x; see x.__class__.__doc__ for signature
  `asc`()
  `between`(cleft, cright)
  `collate`(collation)
  `concat`(other)
  `contains`(other, **kwargs)
  `desc`()
  `distinct`()
  `endswith`(other, **kwargs)
  `ilike`(other, escape=None)
  `in_`(other)
  `like`(other, escape=None)
  `match`(other, **kwargs)
  `op`(opstring)
  `operate`(op, *other, **kwargs)
  `reverse_operate`(op, other, **kwargs)
  `startswith`(other, **kwargs)
  `timetuple`
    Hack, allows datetime objects to be compared on the LHS.

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

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

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

  `__init__`(keyword, *selects, **kwargs)

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()`.

  `execution_options`(**kw)

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

    Current options include:

    - autocommit - when True, a COMMIT will be invoked after execution when executed in ‘autocommit’ mode, i.e. when an explicit transaction is not begun on the connection. Note that DBAPI connections by default are always in a transaction - SQLAlchemy uses rules applied to different kinds of statements to determine if COMMIT will be invoked in order to provide its “autocommit” feature. Typically, all INSERT/UPDATE/DELETE statements as well as CREATE/DROP statements have autocommit behavior enabled; SELECT constructs do not. Use this option when invokving a SELECT or other specific SQL construct where COMMIT is desired (typically when calling stored procedures and such).

    - stream_results - indicate to the dialect that results should be “streamed” and not pre-buffered, if possible. This is a limitation of many DBAPIs. The flag is currently understood only by the psycopg2 dialect.

    - compiled_cache - a dictionary where `Compiled` objects will be cached when the `Connection` compiles a clause expression into a dialect- and parameter-specific `Compiled` object. It is the user’s responsibility to manage the size of this dictionary, which will have keys corresponding to the dialect, clause element, the column names within the VALUES or SET clause of an INSERT or UPDATE, as well as the “batch” mode for an INSERT or UPDATE statement. The format of this dictionary is not guaranteed to stay the same in future releases.

      This option is usually more appropriate to use via the `sqlalchemy.engine.base.Connection.execution_options()` method of `Connection`, rather than upon individual statement objects, though the effect is the same.

    See also:

    > `sqlalchemy.engine.base.Connection.execution_options()`

    > `sqlalchemy.orm.query.Query.execution_options()`

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)

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

  Bases: `sqlalchemy.sql.expression.FunctionElement`

  Describe a named SQL function.

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

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`.

    For table objects, 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 `alias()` method is the general way to create a “subquery” out of an existing SELECT.

    The `name` parameter is optional, and if left blank an “anonymous” name will be generated at compile time, guaranteed to be unique against other anonymous constructs used in the same statement.

  `c`
    Return the collection of Column objects contained by this FromClause.
  `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 occurences 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.

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)
  `alias`(name=None)

    Create a `Select` out of this `Join` clause and return an `Alias` of it.

    The `Select` is not correlating.

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

    Create a `Select` from this `Join`.

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

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

  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 `_SelectBaseMixin` 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`()
    return a new select() construct which will apply DISTINCT to its columns clause.
  `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.
  `prefix_with`(clause)
    return a new select() construct which will apply the given expression to the start of its columns clause, not using any commas.
  `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=None)

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

    The text of the hint is written specific to a specific backend, and typically uses Python string substitution syntax to render the name of the table or alias, such as for Oracle:

        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.``_SelectBaseMixin`(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`

  Base class for `Select` and `CompoundSelects`.

  `__init__`(use_labels=False, for_update=False, limit=None, offset=None, order_by=None, group_by=None, bind=None, autocommit=None)
  `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 True.

    autocommit() is deprecated. Use .execution_options(autocommit=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 “table” construct.

  Note that this represents tables only as another syntactical construct within SQL expressions; it does not provide schema-level functionality.

  `__init__`(name, *columns)
  `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.

## 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)

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

  Bases: `sqlalchemy.sql.functions.GenericFunction`

  `__init__`(**kwargs)

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

  Bases: `sqlalchemy.sql.expression.Function`

  `__init__`(type_=None, args=(), **kwargs)

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

  Bases: `sqlalchemy.sql.functions.GenericFunction`

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

  `__init__`(*args, **kwargs)

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

  Bases: `sqlalchemy.sql.functions.GenericFunction`

  `__init__`(arg, **kwargs)

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

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

  Bases: `sqlalchemy.sql.functions.GenericFunction`

  `__init__`(*args, **kwargs)

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

  Bases: `sqlalchemy.sql.functions.GenericFunction`

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

  `__init__`(expression=None, **kwargs)

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.``now`(type_=None, args=(), **kwargs)
  Bases: `sqlalchemy.sql.functions.GenericFunction`

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

  Bases: `sqlalchemy.sql.functions.GenericFunction`

  `__init__`(*args, **kwargs)

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`