The term “selectable” refers to any object that rows can be selected from; in SQLAlchemy, these objects descend from FromClause and their distinguishing feature is their FromClause.c attribute, which is a namespace of all the columns contained within the FROM clause (these elements are themselves ColumnElement subclasses).
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: |
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Return an EXCEPT of multiple selectables.
The returned object is an instance of CompoundSelect.
Return an EXCEPT ALL of multiple selectables.
The returned object is an instance of CompoundSelect.
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)
Return an INTERSECT of multiple selectables.
The returned object is an instance of CompoundSelect.
Return an INTERSECT ALL of multiple selectables.
The returned object is an instance of CompoundSelect.
Produce a Join object, given two FromClause expressions.
E.g.:
j = join(user_table, address_table, user_table.c.id == address_table.c.user_id)
stmt = select([user_table]).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Similar functionality is available given any FromClause object (e.g. such as a Table) using the FromClause.join() method.
Parameters: |
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See also
FromClause.join() - method form, based on a given left side
Join - the type of object produced
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: |
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To chain joins together, use the FromClause.join() or FromClause.outerjoin() methods on the resulting Join object.
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: |
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Return an Alias object derived from a Select.
*args, **kwargs
all other arguments are delivered to the select() function.
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: |
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See TableClause for further examples.
Return a UNION of multiple selectables.
The returned object is an instance of CompoundSelect.
A similar union() method is available on all FromClause subclasses.
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.
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.
return an alias of this FromClause.
This is shorthand for calling:
from sqlalchemy import alias
a = alias(self, name=name)
See alias() for details.
An alias for the columns attribute.
A named-based collection of ColumnElement objects maintained by this FromClause.
The columns, or c collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:
select([mytable]).where(mytable.c.somecolumn == 5)
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 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: |
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Return corresponding_column for the given column, or if None search for a match in the given dictionary.
Given a ColumnElement, return the exported ColumnElement object from this Selectable which corresponds to that original Column via a common ancestor column.
Parameters: |
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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 ancestor with one of the exported columns of this FromClause.
return a SELECT COUNT generated against this FromClause.
Return the collection of ForeignKey objects which this FromClause references.
Return a Join from this FromClause to another FromClause.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select([user_table]).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Parameters: |
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Return a Join from this FromClause to another FromClause, with the “isouter” flag set to True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id, isouter=True)
Parameters: |
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Return a copy with bindparam() elements 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}
Return the collection of Column objects which comprise the primary key of this FromClause.
replace all occurrences of FromClause ‘old’ with the given Alias object, returning a copy of this FromClause.
return a SELECT of this FromClause.
See also
select() - general purpose method which allows for arbitrary column lists.
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.
Return a copy with bindparam() elements replaced.
Same functionality as params(), except adds unique=True to affected bind parameters so that multiple statements can be used.
Bases: sqlalchemy.sql.expression.SelectBase
return an alias of this FromClause.
This is shorthand for calling:
from sqlalchemy import alias
a = alias(self, name=name)
See alias() for details.
Append the given GROUP BY criterion applied to this selectable.
The criterion will be appended to any pre-existing GROUP BY criterion.
This is an in-place mutation method; the group_by() method is preferred, as it provides standard method chaining.
Append the given ORDER BY criterion applied to this selectable.
The criterion will be appended to any pre-existing ORDER BY criterion.
This is an in-place mutation method; the order_by() method is preferred, as it provides standard method chaining.
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.
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.
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.
An alias for the columns attribute.
A named-based collection of ColumnElement objects maintained by this FromClause.
The columns, or c collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:
select([mytable]).where(mytable.c.somecolumn == 5)
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 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: |
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Return corresponding_column for the given column, or if None search for a match in the given dictionary.
Given a ColumnElement, return the exported ColumnElement object from this Selectable which corresponds to that original Column via a common ancestor column.
Parameters: |
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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 ancestor with one of the exported columns of this FromClause.
return a SELECT COUNT generated against this FromClause.
Return a new CTE, or Common Table Expression instance.
Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
SQLAlchemy detects CTE objects, which are treated similarly to Alias objects, as special elements to be delivered to the FROM clause of the statement as well as to a WITH clause at the top of the statement.
New in version 0.7.6.
Parameters: |
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The following examples illustrate two examples from Postgresql’s documentation at http://www.postgresql.org/docs/8.4/static/queries-with.html.
Example 1, non recursive:
from sqlalchemy import Table, Column, String, Integer, MetaData, \
select, func
metadata = MetaData()
orders = Table('orders', metadata,
Column('region', String),
Column('amount', Integer),
Column('product', String),
Column('quantity', Integer)
)
regional_sales = select([
orders.c.region,
func.sum(orders.c.amount).label('total_sales')
]).group_by(orders.c.region).cte("regional_sales")
top_regions = select([regional_sales.c.region]).\
where(
regional_sales.c.total_sales >
select([
func.sum(regional_sales.c.total_sales)/10
])
).cte("top_regions")
statement = select([
orders.c.region,
orders.c.product,
func.sum(orders.c.quantity).label("product_units"),
func.sum(orders.c.amount).label("product_sales")
]).where(orders.c.region.in_(
select([top_regions.c.region])
)).group_by(orders.c.region, orders.c.product)
result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import Table, Column, String, Integer, MetaData, \
select, func
metadata = MetaData()
parts = Table('parts', metadata,
Column('part', String),
Column('sub_part', String),
Column('quantity', Integer),
)
included_parts = select([
parts.c.sub_part,
parts.c.part,
parts.c.quantity]).\
where(parts.c.part=='our part').\
cte(recursive=True)
incl_alias = included_parts.alias()
parts_alias = parts.alias()
included_parts = included_parts.union_all(
select([
parts_alias.c.sub_part,
parts_alias.c.part,
parts_alias.c.quantity
]).
where(parts_alias.c.part==incl_alias.c.sub_part)
)
statement = select([
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
]).\
group_by(included_parts.c.sub_part)
result = conn.execute(statement).fetchall()
See also
orm.query.Query.cte() - ORM version of SelectBase.cte().
a brief description of this FromClause.
Used primarily for error message formatting.
Compile and execute this Executable.
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.
Return the collection of ForeignKey objects which this FromClause references.
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.
Return a Join from this FromClause to another FromClause.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select([user_table]).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Parameters: |
|
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return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.
See also
return a new selectable with the given LIMIT criterion applied.
return a new selectable with the given OFFSET criterion applied.
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.
Return a Join from this FromClause to another FromClause, with the “isouter” flag set to True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id, isouter=True)
Parameters: |
|
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Return a copy with bindparam() elements 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}
Return the collection of Column objects which comprise the primary key of this FromClause.
replace all occurrences of FromClause ‘old’ with the given Alias object, returning a copy of this FromClause.
Compile and execute this Executable, returning the result’s scalar representation.
return a SELECT of this FromClause.
See also
select() - general purpose method which allows for arbitrary column lists.
Return a copy with bindparam() elements replaced.
Same functionality as params(), except adds unique=True to affected bind parameters so that multiple statements can be used.
Bases: sqlalchemy.sql.expression.Alias
Represent a Common Table Expression.
The CTE object is obtained using the SelectBase.cte() method from any selectable. See that method for complete examples.
New in version 0.7.6.
An alias for the columns attribute.
A named-based collection of ColumnElement objects maintained by this FromClause.
The columns, or c collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:
select([mytable]).where(mytable.c.somecolumn == 5)
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 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: |
|
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Return corresponding_column for the given column, or if None search for a match in the given dictionary.
Given a ColumnElement, return the exported ColumnElement object from this Selectable which corresponds to that original Column via a common ancestor column.
Parameters: |
|
---|
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 ancestor with one of the exported columns of this FromClause.
return a SELECT COUNT generated against this FromClause.
Return the collection of ForeignKey objects which this FromClause references.
Return a Join from this FromClause to another FromClause.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select([user_table]).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Parameters: |
|
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Return a Join from this FromClause to another FromClause, with the “isouter” flag set to True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id, isouter=True)
Parameters: |
|
---|
Return a copy with bindparam() elements 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}
Return the collection of Column objects which comprise the primary key of this FromClause.
replace all occurrences of FromClause ‘old’ with the given Alias object, returning a copy of this FromClause.
return a SELECT of this FromClause.
See also
select() - general purpose method which allows for arbitrary column lists.
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.
Return a copy with bindparam() elements replaced.
Same functionality as params(), except adds unique=True to affected bind parameters so that multiple statements can be used.
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().
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.
Compile and execute this Executable.
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.
Compile and execute this Executable, returning the result’s scalar representation.
Bases: sqlalchemy.sql.expression.Selectable
Represent an element that can be used within the FROM clause of a SELECT statement.
The most common forms of FromClause are the Table and the select() constructs. Key features common to all FromClause objects include:
return an alias of this FromClause.
This is shorthand for calling:
from sqlalchemy import alias
a = alias(self, name=name)
See alias() for details.
A named-based collection of ColumnElement objects maintained by this FromClause.
The columns, or c collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:
select([mytable]).where(mytable.c.somecolumn == 5)
Return corresponding_column for the given column, or if None search for a match in the given dictionary.
Given a ColumnElement, return the exported ColumnElement object from this Selectable which corresponds to that original Column via a common ancestor column.
Parameters: |
|
---|
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 ancestor with one of the exported columns of this FromClause.
return a SELECT COUNT generated against this FromClause.
a brief description of this FromClause.
Used primarily for error message formatting.
Return the collection of ForeignKey objects which this FromClause references.
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.
Return a Join from this FromClause to another FromClause.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select([user_table]).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Parameters: |
|
---|
Return a Join from this FromClause to another FromClause, with the “isouter” flag set to True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id, isouter=True)
Parameters: |
|
---|
Return the collection of Column objects which comprise the primary key of this FromClause.
replace all occurrences of FromClause ‘old’ with the given Alias object, returning a copy of this FromClause.
return a SELECT of this FromClause.
See also
select() - general purpose method which allows for arbitrary column lists.
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.
Construct a new Join.
The usual entrypoint here is the join() function or the FromClause.join() method of any FromClause object.
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.
An alias for the columns attribute.
A named-based collection of ColumnElement objects maintained by this FromClause.
The columns, or c collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:
select([mytable]).where(mytable.c.somecolumn == 5)
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 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: |
|
---|
Return corresponding_column for the given column, or if None search for a match in the given dictionary.
Given a ColumnElement, return the exported ColumnElement object from this Selectable which corresponds to that original Column via a common ancestor column.
Parameters: |
|
---|
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 ancestor with one of the exported columns of this FromClause.
return a SELECT COUNT generated against this FromClause.
Return the collection of ForeignKey objects which this FromClause references.
Return a Join from this FromClause to another FromClause.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select([user_table]).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Parameters: |
|
---|
Return a Join from this FromClause to another FromClause, with the “isouter” flag set to True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id, isouter=True)
Parameters: |
|
---|
Return a copy with bindparam() elements 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}
Return the collection of Column objects which comprise the primary key of this FromClause.
replace all occurrences of FromClause ‘old’ with the given Alias object, returning a copy of this FromClause.
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: |
---|
Return a copy with bindparam() elements replaced.
Same functionality as params(), except adds unique=True to affected bind parameters so that multiple statements can be used.
Bases: sqlalchemy.sql.expression.Generative, sqlalchemy.sql.expression.Grouping
Apply a WHERE clause to the SELECT statement referred to by this ScalarSelect.
Bases: sqlalchemy.sql.expression.HasPrefixes, sqlalchemy.sql.expression.SelectBase
Represents a SELECT statement.
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.
return an alias of this FromClause.
This is shorthand for calling:
from sqlalchemy import alias
a = alias(self, name=name)
See alias() for details.
append the given column expression to the columns clause of this select() construct.
This is an in-place mutation method; the column() method is preferred, as it provides standard method chaining.
append the given correlation expression to this select() construct.
This is an in-place mutation method; the correlate() method is preferred, as it provides standard method chaining.
append the given FromClause expression to this select() construct’s FROM clause.
This is an in-place mutation method; the select_from() method is preferred, as it provides standard method chaining.
Append the given GROUP BY criterion applied to this selectable.
The criterion will be appended to any pre-existing GROUP BY criterion.
This is an in-place mutation method; the group_by() method is preferred, as it provides standard method chaining.
append the given expression to this select() construct’s HAVING criterion.
The expression will be joined to existing HAVING criterion via AND.
This is an in-place mutation method; the having() method is preferred, as it provides standard method chaining.
Append the given ORDER BY criterion applied to this selectable.
The criterion will be appended to any pre-existing ORDER BY criterion.
This is an in-place mutation method; the order_by() method is preferred, as it provides standard method chaining.
append the given columns clause prefix expression to this select() construct.
This is an in-place mutation method; the prefix_with() method is preferred, as it provides standard method chaining.
append the given expression to this select() construct’s WHERE criterion.
The expression will be joined to existing WHERE criterion via AND.
This is an in-place mutation method; the where() method is preferred, as it provides standard method chaining.
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.
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.
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.
An alias for the columns attribute.
return a new select() construct with the given column expression added to its columns clause.
A named-based collection of ColumnElement objects maintained by this FromClause.
The columns, or c collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:
select([mytable]).where(mytable.c.somecolumn == 5)
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 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: |
|
---|
return a new Select which will correlate the given FROM clauses to that of an enclosing Select.
Calling this method turns off the Select object’s default behavior of “auto-correlation”. Normally, FROM elements which appear in a Select that encloses this one via its WHERE clause, ORDER BY, HAVING or columns clause will be omitted from this Select object’s FROM clause. Setting an explicit correlation collection using the Select.correlate() method provides a fixed list of FROM objects that can potentially take place in this process.
When Select.correlate() is used to apply specific FROM clauses for correlation, the FROM elements become candidates for correlation regardless of how deeply nested this Select object is, relative to an enclosing Select which refers to the same FROM object. This is in contrast to the behavior of “auto-correlation” which only correlates to an immediate enclosing Select. Multi-level correlation ensures that the link between enclosed and enclosing Select is always via at least one WHERE/ORDER BY/HAVING/columns clause in order for correlation to take place.
If None is passed, the Select object will correlate none of its FROM entries, and all will render unconditionally in the local FROM clause.
Parameters: | *fromclauses¶ – a list of one or more FromClause constructs, or other compatible constructs (i.e. ORM-mapped classes) to become part of the correlate collection. Changed in version 0.8.0: ORM-mapped classes are accepted by Select.correlate(). |
---|
Changed in version 0.8.0: The Select.correlate() method no longer unconditionally removes entries from the FROM clause; instead, the candidate FROM entries must also be matched by a FROM entry located in an enclosing Select, which ultimately encloses this one as present in the WHERE clause, ORDER BY clause, HAVING clause, or columns clause of an enclosing Select().
return a new Select which will omit the given FROM clauses from the auto-correlation process.
Calling Select.correlate_except() turns off the Select object’s default behavior of “auto-correlation” for the given FROM elements. An element specified here will unconditionally appear in the FROM list, while all other FROM elements remain subject to normal auto-correlation behaviors.
Changed in version 0.8.2: The Select.correlate_except() method was improved to fully prevent FROM clauses specified here from being omitted from the immediate FROM clause of this Select.
If None is passed, the Select object will correlate all of its FROM entries.
Changed in version 0.8.2: calling correlate_except(None) will correctly auto-correlate all FROM clauses.
Parameters: | *fromclauses¶ – a list of one or more FromClause constructs, or other compatible constructs (i.e. ORM-mapped classes) to become part of the correlate-exception collection. |
---|
Return corresponding_column for the given column, or if None search for a match in the given dictionary.
Given a ColumnElement, return the exported ColumnElement object from this Selectable which corresponds to that original Column via a common ancestor column.
Parameters: |
|
---|
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 ancestor with one of the exported columns of this FromClause.
return a SELECT COUNT generated against this FromClause.
Return a new CTE, or Common Table Expression instance.
Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
SQLAlchemy detects CTE objects, which are treated similarly to Alias objects, as special elements to be delivered to the FROM clause of the statement as well as to a WITH clause at the top of the statement.
New in version 0.7.6.
Parameters: |
|
---|
The following examples illustrate two examples from Postgresql’s documentation at http://www.postgresql.org/docs/8.4/static/queries-with.html.
Example 1, non recursive:
from sqlalchemy import Table, Column, String, Integer, MetaData, \
select, func
metadata = MetaData()
orders = Table('orders', metadata,
Column('region', String),
Column('amount', Integer),
Column('product', String),
Column('quantity', Integer)
)
regional_sales = select([
orders.c.region,
func.sum(orders.c.amount).label('total_sales')
]).group_by(orders.c.region).cte("regional_sales")
top_regions = select([regional_sales.c.region]).\
where(
regional_sales.c.total_sales >
select([
func.sum(regional_sales.c.total_sales)/10
])
).cte("top_regions")
statement = select([
orders.c.region,
orders.c.product,
func.sum(orders.c.quantity).label("product_units"),
func.sum(orders.c.amount).label("product_sales")
]).where(orders.c.region.in_(
select([top_regions.c.region])
)).group_by(orders.c.region, orders.c.product)
result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import Table, Column, String, Integer, MetaData, \
select, func
metadata = MetaData()
parts = Table('parts', metadata,
Column('part', String),
Column('sub_part', String),
Column('quantity', Integer),
)
included_parts = select([
parts.c.sub_part,
parts.c.part,
parts.c.quantity]).\
where(parts.c.part=='our part').\
cte(recursive=True)
incl_alias = included_parts.alias()
parts_alias = parts.alias()
included_parts = included_parts.union_all(
select([
parts_alias.c.sub_part,
parts_alias.c.part,
parts_alias.c.quantity
]).
where(parts_alias.c.part==incl_alias.c.sub_part)
)
statement = select([
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
]).\
group_by(included_parts.c.sub_part)
result = conn.execute(statement).fetchall()
See also
orm.query.Query.cte() - ORM version of SelectBase.cte().
a brief description of this FromClause.
Used primarily for error message formatting.
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. |
---|
return a SQL EXCEPT of this select() construct against the given selectable.
return a SQL EXCEPT ALL of this select() construct against the given selectable.
Compile and execute this Executable.
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.
Return the collection of ForeignKey objects which this FromClause references.
Return the displayed list of FromClause elements.
return child elements as per the ClauseElement specification.
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.
return a new select() construct with the given expression added to its HAVING clause, joined to the existing clause via AND, if any.
an iterator of all ColumnElement expressions which would be rendered into the columns clause of the resulting SELECT statement.
return a SQL INTERSECT of this select() construct against the given selectable.
return a SQL INTERSECT ALL of this select() construct against the given selectable.
Return a Join from this FromClause to another FromClause.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select([user_table]).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Parameters: |
|
---|
return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.
See also
return a new selectable with the given LIMIT criterion applied.
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.
return a new selectable with the given OFFSET criterion applied.
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.
Return a Join from this FromClause to another FromClause, with the “isouter” flag set to True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id, isouter=True)
Parameters: |
|
---|
Return a copy with bindparam() elements 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}
Add one or more expressions following the statement keyword, i.e. SELECT, INSERT, UPDATE, or DELETE. Generative.
This is used to support backend-specific prefix keywords such as those provided by MySQL.
E.g.:
stmt = table.insert().prefix_with("LOW_PRIORITY", dialect="mysql")
Multiple prefixes can be specified by multiple calls to prefix_with().
Parameters: |
|
---|
Return the collection of Column objects which comprise the primary key of this FromClause.
Return a new :func`.select` construct with redundantly named, equivalently-valued columns removed from the columns clause.
“Redundant” here means two columns where one refers to the other either based on foreign key, or via a simple equality comparison in the WHERE clause of the statement. The primary purpose of this method is to automatically construct a select statement with all uniquely-named columns, without the need to use table-qualified labels as apply_labels() does.
When columns are omitted based on foreign key, the referred-to column is the one that’s kept. When columns are omitted based on WHERE eqivalence, the first column in the columns clause is the one that’s kept.
Parameters: | only_synonyms¶ – when True, limit the removal of columns to those which have the same name as the equivalent. Otherwise, all columns that are equivalent to another are removed. |
---|
New in version 0.8.
replace all occurrences of FromClause ‘old’ with the given Alias object, returning a copy of this FromClause.
Compile and execute this Executable, returning the result’s scalar representation.
return a SELECT of this FromClause.
See also
select() - general purpose method which allows for arbitrary column lists.
return a new select() construct with the given FROM expression merged into its list of FROM objects.
E.g.:
table1 = table('t1', column('a'))
table2 = table('t2', column('b'))
s = select([table1.c.a]).\
select_from(
table1.join(table2, table1.c.a==table2.c.b)
)
The “from” list is a unique set on the identity of each element, so adding an already present Table or other selectable will have no effect. Passing a Join that refers to an already present Table or other selectable will have the effect of concealing the presence of that selectable as an individual element in the rendered FROM list, instead rendering it into a JOIN clause.
While the typical purpose of Select.select_from() is to replace the default, derived FROM clause with a join, it can also be called with individual table elements, multiple times if desired, in the case that the FROM clause cannot be fully derived from the columns clause:
select([func.count('*')]).select_from(table1)
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 and should not require explicit use.
return a SQL UNION of this select() construct against the given selectable.
return a SQL UNION ALL of this select() construct against the given selectable.
Return a copy with bindparam() elements replaced.
Same functionality as params(), except adds unique=True to affected bind parameters so that multiple statements can be used.
return a new select() construct with the given expression added to its WHERE clause, joined to the existing clause via AND, if any.
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')
Return a new select() construct with its columns clause replaced with the given columns.
Changed in version 0.7.3: Due to a bug fix, this method has a slight behavioral change as of version 0.7.3. Prior to version 0.7.3, the FROM clause of a select() was calculated upfront and as new columns were added; in 0.7.3 and later it’s calculated at compile time, fixing an issue regarding late binding of columns to parent tables. This changes the behavior of Select.with_only_columns() in that FROM clauses no longer represented in the new list are dropped, but this behavior is more consistent in that the FROM clauses are consistently derived from the current columns clause. The original intent of this method is to allow trimming of the existing columns list to be fewer columns than originally present; the use case of replacing the columns list with an entirely different one hadn’t been anticipated until 0.7.3 was released; the usage guidelines below illustrate how this should be done.
This method is exactly equivalent to as if the original select() had been called with the given columns clause. I.e. a statement:
s = select([table1.c.a, table1.c.b])
s = s.with_only_columns([table1.c.b])
should be exactly equivalent to:
s = select([table1.c.b])
This means that FROM clauses which are only derived from the column list will be discarded if the new column list no longer contains that FROM:
>>> table1 = table('t1', column('a'), column('b'))
>>> table2 = table('t2', column('a'), column('b'))
>>> s1 = select([table1.c.a, table2.c.b])
>>> print s1
SELECT t1.a, t2.b FROM t1, t2
>>> s2 = s1.with_only_columns([table2.c.b])
>>> print s2
SELECT t2.b FROM t1
The preferred way to maintain a specific FROM clause in the construct, assuming it won’t be represented anywhere else (i.e. not in the WHERE clause, etc.) is to set it using Select.select_from():
>>> s1 = select([table1.c.a, table2.c.b]).\
... select_from(table1.join(table2,
... table1.c.a==table2.c.a))
>>> s2 = s1.with_only_columns([table2.c.b])
>>> print s2
SELECT t2.b FROM t1 JOIN t2 ON t1.a=t2.a
Care should also be taken to use the correct set of column objects passed to Select.with_only_columns(). Since the method is essentially equivalent to calling the select() construct in the first place with the given columns, the columns passed to Select.with_only_columns() should usually be a subset of those which were passed to the select() construct, not those which are available from the .c collection of that select(). That is:
s = select([table1.c.a, table1.c.b]).select_from(table1)
s = s.with_only_columns([table1.c.b])
and not:
# usually incorrect
s = s.with_only_columns([s.c.b])
The latter would produce the SQL:
SELECT b
FROM (SELECT t1.a AS a, t1.b AS b
FROM t1), t1
Since the select() construct is essentially being asked to select both from table1 as well as itself.
Bases: sqlalchemy.sql.expression.ClauseElement
mark a class as being selectable
Bases: sqlalchemy.sql.expression.Executable, sqlalchemy.sql.expression.FromClause
Base class for Select and CompoundSelect.
Append the given GROUP BY criterion applied to this selectable.
The criterion will be appended to any pre-existing GROUP BY criterion.
This is an in-place mutation method; the group_by() method is preferred, as it provides standard method chaining.
Append the given ORDER BY criterion applied to this selectable.
The criterion will be appended to any pre-existing ORDER BY criterion.
This is an in-place mutation method; the order_by() method is preferred, as it provides standard method chaining.
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.
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.
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.
Return a new CTE, or Common Table Expression instance.
Common table expressions are a SQL standard whereby SELECT statements can draw upon secondary statements specified along with the primary statement, using a clause called “WITH”. Special semantics regarding UNION can also be employed to allow “recursive” queries, where a SELECT statement can draw upon the set of rows that have previously been selected.
SQLAlchemy detects CTE objects, which are treated similarly to Alias objects, as special elements to be delivered to the FROM clause of the statement as well as to a WITH clause at the top of the statement.
New in version 0.7.6.
Parameters: |
|
---|
The following examples illustrate two examples from Postgresql’s documentation at http://www.postgresql.org/docs/8.4/static/queries-with.html.
Example 1, non recursive:
from sqlalchemy import Table, Column, String, Integer, MetaData, \
select, func
metadata = MetaData()
orders = Table('orders', metadata,
Column('region', String),
Column('amount', Integer),
Column('product', String),
Column('quantity', Integer)
)
regional_sales = select([
orders.c.region,
func.sum(orders.c.amount).label('total_sales')
]).group_by(orders.c.region).cte("regional_sales")
top_regions = select([regional_sales.c.region]).\
where(
regional_sales.c.total_sales >
select([
func.sum(regional_sales.c.total_sales)/10
])
).cte("top_regions")
statement = select([
orders.c.region,
orders.c.product,
func.sum(orders.c.quantity).label("product_units"),
func.sum(orders.c.amount).label("product_sales")
]).where(orders.c.region.in_(
select([top_regions.c.region])
)).group_by(orders.c.region, orders.c.product)
result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE:
from sqlalchemy import Table, Column, String, Integer, MetaData, \
select, func
metadata = MetaData()
parts = Table('parts', metadata,
Column('part', String),
Column('sub_part', String),
Column('quantity', Integer),
)
included_parts = select([
parts.c.sub_part,
parts.c.part,
parts.c.quantity]).\
where(parts.c.part=='our part').\
cte(recursive=True)
incl_alias = included_parts.alias()
parts_alias = parts.alias()
included_parts = included_parts.union_all(
select([
parts_alias.c.sub_part,
parts_alias.c.part,
parts_alias.c.quantity
]).
where(parts_alias.c.part==incl_alias.c.sub_part)
)
statement = select([
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
]).\
group_by(included_parts.c.sub_part)
result = conn.execute(statement).fetchall()
See also
orm.query.Query.cte() - ORM version of SelectBase.cte().
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.
return a ‘scalar’ representation of this selectable, embedded as a subquery with a label.
See also
return a new selectable with the given LIMIT criterion applied.
return a new selectable with the given OFFSET criterion applied.
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.
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.
return an alias of this FromClause.
This is shorthand for calling:
from sqlalchemy import alias
a = alias(self, name=name)
See alias() for details.
An alias for the columns attribute.
A named-based collection of ColumnElement objects maintained by this FromClause.
The columns, or c collection, is the gateway to the construction of SQL expressions using table-bound or other selectable-bound columns:
select([mytable]).where(mytable.c.somecolumn == 5)
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 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: |
|
---|
Return corresponding_column for the given column, or if None search for a match in the given dictionary.
Given a ColumnElement, return the exported ColumnElement object from this Selectable which corresponds to that original Column via a common ancestor column.
Parameters: |
|
---|
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 ancestor with one of the exported columns of this FromClause.
return a SELECT COUNT generated against this TableClause.
Generate a delete() construct against this TableClause.
E.g.:
table.delete().where(table.c.id==7)
See delete() for argument and usage information.
Return the collection of ForeignKey objects which this FromClause references.
TableClause doesn’t support having a primary key or column -level defaults, so implicit returning doesn’t apply.
Generate an insert() construct against this TableClause.
E.g.:
table.insert().values(name='foo')
See insert() for argument and usage information.
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.
Return a Join from this FromClause to another FromClause.
E.g.:
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select([user_table]).select_from(j)
would emit SQL along the lines of:
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
Parameters: |
|
---|
Return a Join from this FromClause to another FromClause, with the “isouter” flag set to True.
E.g.:
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to:
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id, isouter=True)
Parameters: |
|
---|
Return the collection of Column objects which comprise the primary key of this FromClause.
replace all occurrences of FromClause ‘old’ with the given Alias object, returning a copy of this FromClause.
return a SELECT of this FromClause.
See also
select() - general purpose method which allows for arbitrary column lists.
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.
Generate an update() construct against this TableClause.
E.g.:
table.update().where(table.c.id==7).values(name='foo')
See update() for argument and usage information.