SQL Statements and Expressions API
Selectables, Tables, FROM objects
The most fundamental part of the SQL expression API are the “column elements”, which allow for basic SQL expression support. The core of all SQL expression constructs is the ClauseElement, which is the base for several sub-branches. The ColumnElement class is the fundamental unit used to construct any kind of typed SQL expression.
Join a list of clauses together using the AND operator.
The & operator is also overloaded on all ColumnElement subclasses to produce the same result.
Return an ascending ORDER BY clause element.
e.g.:
someselect.order_by(asc(table1.mycol))
produces:
ORDER BY mycol ASC
Return a BETWEEN predicate clause.
Equivalent of SQL clausetest BETWEEN clauseleft AND clauseright.
The between() method on all ColumnElement subclasses provides similar functionality.
Construct a new BindParameter.
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Produce a Case object.
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The expressions used for THEN and ELSE, when specified as strings, will be interpreted as bound values. To specify textual SQL expressions for these, use the literal_column() construct.
The expressions used for the WHEN criterion may only be literal strings when “value” is present, i.e. CASE table.somecol WHEN “x” THEN “y”. Otherwise, literal strings are not accepted in this position, and either the text(<string>) or literal(<string>) constructs must be used to interpret raw string values.
Usage examples:
case([(orderline.c.qty > 100, item.c.specialprice),
(orderline.c.qty > 10, item.c.bulkprice)
], else_=item.c.regularprice)
case(value=emp.c.type, whens={
'engineer': emp.c.salary * 1.1,
'manager': emp.c.salary * 3,
})
Using literal_column(), to allow for databases that do not support bind parameters in the then clause. The type can be specified which determines the type of the case() construct overall:
case([(orderline.c.qty > 100,
literal_column("'greaterthan100'", String)),
(orderline.c.qty > 10, literal_column("'greaterthan10'",
String))
], else_=literal_column("'lethan10'", String))
Return a Cast object.
Equivalent of SQL CAST(clause AS totype).
E.g.:
cast(table.c.unit_price * table.c.qty, Numeric(10,4))
or:
cast(table.c.timestamp, DATE)
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See also
type_coerce() - Python-side type coercion without emitting CAST.
Construct a ColumnClause object.
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Return the clause expression COLLATE collation.
e.g.:
collate(mycolumn, 'utf8_bin')
produces:
mycolumn COLLATE utf8_bin
Return a descending ORDER BY clause element.
e.g.:
someselect.order_by(desc(table1.mycol))
produces:
ORDER BY mycol DESC
Return a DISTINCT clause.
e.g.:
distinct(a)
renders:
DISTINCT a
Return a Extract construct.
This is typically available as extract() as well as func.extract from the func namespace.
Return a constant False_ construct.
E.g.:
>>> from sqlalchemy import false
>>> print select([t.c.x]).where(false())
SELECT x FROM t WHERE false
A backend which does not support true/false constants will render as an expression against 1 or 0:
>>> print select([t.c.x]).where(false())
SELECT x FROM t WHERE 0 = 1
The true() and false() constants also feature “short circuit” operation within an and_() or or_() conjunction:
>>> print select([t.c.x]).where(or_(t.c.x > 5, true()))
SELECT x FROM t WHERE true
>>> print select([t.c.x]).where(and_(t.c.x > 5, false()))
SELECT x FROM t WHERE false
Changed in version 0.9: true() and false() feature better integrated behavior within conjunctions and on dialects that don’t support true/false constants.
See also
Generate SQL function expressions.
func is a special object instance which generates SQL functions based on name-based attributes, e.g.:
>>> print func.count(1)
count(:param_1)
The element is a column-oriented SQL element like any other, and is used in that way:
>>> print select([func.count(table.c.id)])
SELECT count(sometable.id) FROM sometable
Any name can be given to func. If the function name is unknown to SQLAlchemy, it will be rendered exactly as is. For common SQL functions which SQLAlchemy is aware of, the name may be interpreted as a generic function which will be compiled appropriately to the target database:
>>> print func.current_timestamp()
CURRENT_TIMESTAMP
To call functions which are present in dot-separated packages, specify them in the same manner:
>>> print func.stats.yield_curve(5, 10)
stats.yield_curve(:yield_curve_1, :yield_curve_2)
SQLAlchemy can be made aware of the return type of functions to enable type-specific lexical and result-based behavior. For example, to ensure that a string-based function returns a Unicode value and is similarly treated as a string in expressions, specify Unicode as the type:
>>> print func.my_string(u'hi', type_=Unicode) + ' ' + \
... func.my_string(u'there', type_=Unicode)
my_string(:my_string_1) || :my_string_2 || my_string(:my_string_3)
The object returned by a func call is usually an instance of Function. This object meets the “column” interface, including comparison and labeling functions. The object can also be passed the execute() method of a Connection or Engine, where it will be wrapped inside of a SELECT statement first:
print connection.execute(func.current_timestamp()).scalar()
In a few exception cases, the func accessor will redirect a name to a built-in expression such as cast() or extract(), as these names have well-known meaning but are not exactly the same as “functions” from a SQLAlchemy perspective.
New in version 0.8: func can return non-function expression constructs for common quasi-functional names like cast() and extract().
Functions which are interpreted as “generic” functions know how to calculate their return type automatically. For a listing of known generic functions, see SQL and Generic Functions.
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 ColumnElement.label() method on ColumnElement.
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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 ColumnElement subclass, such as a Column object. Use this function to force the generation of a literal clause, which will be created as a BindParameter with a bound value.
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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).
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Return a negation of the given clause, i.e. NOT(clause).
The ~ operator is also overloaded on all ColumnElement subclasses to produce the same result.
Return a NULLS FIRST ORDER BY clause element.
e.g.:
someselect.order_by(desc(table1.mycol).nullsfirst())
produces:
ORDER BY mycol DESC NULLS FIRST
Return a NULLS LAST ORDER BY clause element.
e.g.:
someselect.order_by(desc(table1.mycol).nullslast())
produces:
ORDER BY mycol DESC NULLS LAST
Join a list of clauses together using the OR operator.
The | operator is also overloaded on all ColumnElement subclasses to produce the same result.
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.
Produce an Over object against a function.
Used against aggregate or so-called “window” functions, for database backends that support window functions.
E.g.:
from sqlalchemy import over
over(func.row_number(), order_by='x')
Would produce “ROW_NUMBER() OVER(ORDER BY x)”.
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This function is also available from the func construct itself via the FunctionElement.over() method.
New in version 0.7.
Construct a new TextClause clause, representing a textual SQL string directly.
E.g.:
fom sqlalchemy import text
t = text("SELECT * FROM users")
result = connection.execute(t)
The advantages text() provides over a plain string are backend-neutral support for bind parameters, per-statement execution options, as well as bind parameter and result-column typing behavior, allowing SQLAlchemy type constructs to play a role when executing a statement that is specified literally. The construct can also be provided with a .c collection of column elements, allowing it to be embedded in other SQL expression constructs as a subquery.
Bind parameters are specified by name, using the format :name. E.g.:
t = text("SELECT * FROM users WHERE id=:user_id")
result = connection.execute(t, user_id=12)
For SQL statements where a colon is required verbatim, as within an inline string, use a backslash to escape:
t = text("SELECT * FROM users WHERE name='\:username'")
The TextClause construct includes methods which can provide information about the bound parameters as well as the column values which would be returned from the textual statement, assuming it’s an executable SELECT type of statement. The TextClause.bindparams() method is used to provide bound parameter detail, and TextClause.columns() method allows specification of return columns including names and types:
t = text("SELECT * FROM users WHERE id=:user_id").\
bindparams(user_id=7).\
columns(id=Integer, name=String)
for id, name in connection.execute(t):
print(id, name)
The text() construct is used internally in cases when a literal string is specified for part of a larger query, such as when a string is specified to the Select.where() method of Select. In those cases, the same bind parameter syntax is applied:
s = select([users.c.id, users.c.name]).where("id=:user_id")
result = connection.execute(s, user_id=12)
Using text() explicitly usually implies the construction of a full, standalone statement. As such, SQLAlchemy refers to it as an Executable object, and it supports the Executable.execution_options() method. For example, a text() construct that should be subject to “autocommit” can be set explicitly so using the autocommit option:
t = text("EXEC my_procedural_thing()").\
execution_options(autocommit=True)
Note that SQLAlchemy’s usual “autocommit” behavior applies to text() constructs implicitly - that is, statements which begin with a phrase such as INSERT, UPDATE, DELETE, or a variety of other phrases specific to certain backends, will be eligible for autocommit if no transaction is in progress.
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Return a constant True_ construct.
E.g.:
>>> from sqlalchemy import true
>>> print select([t.c.x]).where(true())
SELECT x FROM t WHERE true
A backend which does not support true/false constants will render as an expression against 1 or 0:
>>> print select([t.c.x]).where(true())
SELECT x FROM t WHERE 1 = 1
The true() and false() constants also feature “short circuit” operation within an and_() or or_() conjunction:
>>> print select([t.c.x]).where(or_(t.c.x > 5, true()))
SELECT x FROM t WHERE true
>>> print select([t.c.x]).where(and_(t.c.x > 5, false()))
SELECT x FROM t WHERE false
Changed in version 0.9: true() and false() feature better integrated behavior within conjunctions and on dialects that don’t support true/false constants.
See also
Return a Tuple.
Main usage is to produce a composite IN construct:
from sqlalchemy import tuple_
tuple_(table.c.col1, table.c.col2).in_(
[(1, 2), (5, 12), (10, 19)]
)
Warning
The composite IN construct is not supported by all backends, and is currently known to work on Postgresql and MySQL, but not SQLite. Unsupported backends will raise a subclass of DBAPIError when such an expression is invoked.
Coerce the given expression into the given type, on the Python side only.
type_coerce() is roughly similar to cast(), except no “CAST” expression is rendered - the given type is only applied towards expression typing and against received result values.
e.g.:
from sqlalchemy.types import TypeDecorator
import uuid
class AsGuid(TypeDecorator):
impl = String
def process_bind_param(self, value, dialect):
if value is not None:
return str(value)
else:
return None
def process_result_value(self, value, dialect):
if value is not None:
return uuid.UUID(value)
else:
return None
conn.execute(
select([type_coerce(mytable.c.ident, AsGuid)]).\
where(
type_coerce(mytable.c.ident, AsGuid) ==
uuid.uuid3(uuid.NAMESPACE_URL, 'bar')
)
)
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See also
Bases: sqlalchemy.sql.expression.ColumnElement
Represent an expression that is LEFT <operator> RIGHT.
A BinaryExpression is generated automatically whenever two column expressions are used in a Python binary expresion:
>>> from sqlalchemy.sql import column
>>> column('a') + column('b')
<sqlalchemy.sql.expression.BinaryExpression object at 0x101029dd0>
>>> print column('a') + column('b')
a + b
Compare this BinaryExpression against the given BinaryExpression.
Bases: sqlalchemy.sql.expression.ColumnElement
Represent a bound parameter value.
Construct a new BindParameter object.
This constructor is mirrored as a public API function; see bindparam() for a full usage and argument description.
Compare this BindParameter to the given clause.
Return the value of this bound parameter, taking into account if the callable parameter was set.
The callable value will be evaluated and returned if present, else value.
Bases: sqlalchemy.sql.expression.ColumnElement
Represent a SQL CASE construct.
Bases: sqlalchemy.sql.expression.ColumnElement
Represent the SQL CAST construct.
Bases: sqlalchemy.sql.visitors.Visitable
Base class for elements of a programmatically constructed SQL expression.
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.
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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).
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}
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.ClauseElement
Describe a list of clauses, separated by an operator.
By default, is comma-separated, such as a column listing.
Compare this ClauseList to the given ClauseList, including a comparison of all the clause items.
Bases: sqlalchemy.sql.expression.Immutable, sqlalchemy.sql.expression.ColumnElement
Represents a generic column expression from any textual string.
This includes columns associated with tables, aliases and select statements, but also any arbitrary text. May or may not be bound to an underlying Selectable.
ColumnClause is constructed by itself typically via the column() function. It may be placed directly into constructs such as select() constructs:
from sqlalchemy.sql import column, select
c1, c2 = column("c1"), column("c2")
s = select([c1, c2]).where(c1==5)
There is also a variant on column() known as literal_column() - the difference is that in the latter case, the string value is assumed to be an exact expression, rather than a column name, so that no quoting rules or similar are applied:
from sqlalchemy.sql import literal_column, select
s = select([literal_column("5 + 7")])
ColumnClause can also be used in a table-like fashion by combining the column() function with the table() function, to produce a “lightweight” form of table metadata:
from sqlalchemy.sql import table, column
user = table("user",
column("id"),
column("name"),
column("description"),
)
The above construct can be created in an ad-hoc fashion and is not associated with any schema.MetaData, unlike it’s more full fledged schema.Table counterpart.
Construct a new ColumnClause object.
This constructor is mirrored as a public API function; see column() for a full usage and argument description.
Bases: sqlalchemy.util._collections.OrderedProperties
An ordered dictionary that stores a list of ColumnElement instances.
Overrides the __eq__() method to produce SQL clauses between sets of correlated columns.
Add a column to this collection.
The key attribute of the column will be used as the hash key for this dictionary.
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.
Bases: sqlalchemy.sql.expression.ClauseElement, sqlalchemy.sql.operators.ColumnOperators
Represent a column-oriented SQL expression suitable for usage in the “columns” clause, WHERE clause etc. of a statement.
While the most familiar kind of ColumnElement is the Column object, ColumnElement serves as the basis for any unit that may be present in a SQL expression, including the expressions themselves, SQL functions, bound parameters, literal expressions, keywords such as NULL, etc. ColumnElement is the ultimate base class for all such elements.
A ColumnElement provides the ability to generate new ColumnElement objects using Python expressions. This means that Python operators such as ==, != and < are overloaded to mimic SQL operations, and allow the instantiation of further ColumnElement instances which are composed from other, more fundamental ColumnElement objects. For example, two ColumnClause objects can be added together with the addition operator + to produce a BinaryExpression. Both ColumnClause and BinaryExpression are subclasses of ColumnElement:
>>> from sqlalchemy.sql import column
>>> column('a') + column('b')
<sqlalchemy.sql.expression.BinaryExpression object at 0x101029dd0>
>>> print column('a') + column('b')
a + b
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. For the ambitious, an in-depth discussion of this concept can be found at Expression Transformations.
Implement the == operator.
In a column context, produces the clause a = b. If the target is None, produces a IS NULL.
x.__init__(...) initializes x; see help(type(x)) for signature
Implement the <= operator.
In a column context, produces the clause a <= b.
Implement the < operator.
In a column context, produces the clause a < b.
Implement the != operator.
In a column context, produces the clause a != b. If the target is None, produces a IS NOT NULL.
provides a constant ‘anonymous label’ for this ColumnElement.
This is a label() expression which will be named at compile time. The same label() is returned each time anon_label is called so that expressions can reference anon_label multiple times, producing the same label name at compile time.
the compiler uses this function automatically at compile time for expressions that are known to be ‘unnamed’ like binary expressions and function calls.
Produce a asc() clause against the parent object.
Produce a between() clause against the parent object, given the lower and upper range.
Produce a collate() clause against the parent object, given the collation string.
Compare this ColumnElement to another.
Special arguments understood:
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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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Implement the ‘concat’ operator.
In a column context, produces the clause a || b, or uses the concat() operator on MySQL.
Implement the ‘contains’ operator.
In a column context, produces the clause LIKE '%<other>%'
Produce a desc() clause against the parent object.
Produce a distinct() clause against the parent object.
Implement the ‘endswith’ operator.
In a column context, produces the clause LIKE '%<other>'
Return a column expression.
Part of the inspection interface; returns self.
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).
Implement the ilike operator.
In a column context, produces the clause a ILIKE other.
E.g.:
select([sometable]).where(sometable.c.column.ilike("%foobar%"))
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See also
Implement the in operator.
In a column context, produces the clause a IN other. “other” may be a tuple/list of column expressions, or a select() construct.
Implement the IS operator.
Normally, IS is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS may be desirable if comparing to boolean values on certain platforms.
New in version 0.7.9.
See also
Implement the IS NOT operator.
Normally, IS NOT is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS NOT may be desirable if comparing to boolean values on certain platforms.
New in version 0.7.9.
See also
Produce a column label, i.e. <columnname> AS <name>.
This is a shortcut to the label() function.
if ‘name’ is None, an anonymous label name will be generated.
Implement the like operator.
In a column context, produces the clause a LIKE other.
E.g.:
select([sometable]).where(sometable.c.column.like("%foobar%"))
Parameters: |
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See also
Implements the ‘match’ operator.
In a column context, this produces a MATCH clause, i.e. MATCH '<other>'. The allowed contents of other are database backend specific.
implement the NOT ILIKE operator.
This is equivalent to using negation with ColumnOperators.ilike(), i.e. ~x.ilike(y).
New in version 0.8.
See also
implement the NOT IN operator.
This is equivalent to using negation with ColumnOperators.in_(), i.e. ~x.in_(y).
New in version 0.8.
See also
implement the NOT LIKE operator.
This is equivalent to using negation with ColumnOperators.like(), i.e. ~x.like(y).
New in version 0.8.
See also
Produce a nullsfirst() clause against the parent object.
Produce a nullslast() clause against the parent object.
produce a generic operator function.
e.g.:
somecolumn.op("*")(5)
produces:
somecolumn * 5
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.
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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 True if the given ColumnElement has a common ancestor to this ColumnElement.
Implement the startwith operator.
In a column context, produces the clause LIKE '<other>%'
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.operators.Operators
Defines boolean, comparison, and other operators for ColumnElement expressions.
By default, all methods call down to operate() or reverse_operate(), passing in the appropriate operator function from the Python builtin operator module or a SQLAlchemy-specific operator function from sqlalchemy.expression.operators. For example the __eq__ function:
def __eq__(self, other):
return self.operate(operators.eq, other)
Where operators.eq is essentially:
def eq(a, b):
return a == b
The core column expression unit ColumnElement overrides Operators.operate() and others to return further ColumnElement constructs, so that the == operation above is replaced by a clause construct.
See also:
Redefining and Creating New Operators
Implement the + operator.
In a column context, produces the clause a + b if the parent object has non-string affinity. If the parent object has a string affinity, produces the concatenation operator, a || b - see ColumnOperators.concat().
Implement the & operator.
When used with SQL expressions, results in an AND operation, equivalent to and_(), that is:
a & b
is equivalent to:
from sqlalchemy import and_
and_(a, b)
Care should be taken when using & regarding operator precedence; the & operator has the highest precedence. The operands should be enclosed in parenthesis if they contain further sub expressions:
(a == 2) & (b == 4)
x.__delattr__(‘name’) <==> del x.name
Implement the / operator.
In a column context, produces the clause a / b.
Implement the == operator.
In a column context, produces the clause a = b. If the target is None, produces a IS NULL.
default object formatter
Implement the >= operator.
In a column context, produces the clause a >= b.
x.__getattribute__(‘name’) <==> x.name
Implement the [] operator.
This can be used by some database-specific types such as Postgresql ARRAY and HSTORE.
Implement the > operator.
In a column context, produces the clause a > b.
x.__hash__() <==> hash(x)
x.__init__(...) initializes x; see help(type(x)) for signature
Implement the ~ operator.
When used with SQL expressions, results in a NOT operation, equivalent to not_(), that is:
~a
is equivalent to:
from sqlalchemy import not_
not_(a)
Implement the <= operator.
In a column context, produces the clause a <= b.
implement the << operator.
Not used by SQLAlchemy core, this is provided for custom operator systems which want to use << as an extension point.
Implement the < operator.
In a column context, produces the clause a < b.
Implement the % operator.
In a column context, produces the clause a % b.
Implement the * operator.
In a column context, produces the clause a * b.
Implement the != operator.
In a column context, produces the clause a != b. If the target is None, produces a IS NOT NULL.
Implement the - operator.
In a column context, produces the clause -a.
Implement the | operator.
When used with SQL expressions, results in an OR operation, equivalent to or_(), that is:
a | b
is equivalent to:
from sqlalchemy import or_
or_(a, b)
Care should be taken when using | regarding operator precedence; the | operator has the highest precedence. The operands should be enclosed in parenthesis if they contain further sub expressions:
(a == 2) | (b == 4)
Implement the + operator in reverse.
Implement the / operator in reverse.
helper for pickle
helper for pickle
x.__repr__() <==> repr(x)
Implement the * operator in reverse.
implement the >> operator.
Not used by SQLAlchemy core, this is provided for custom operator systems which want to use >> as an extension point.
Implement the - operator in reverse.
Implement the // operator in reverse.
x.__setattr__(‘name’, value) <==> x.name = value
size of object in memory, in bytes
x.__str__() <==> str(x)
Implement the - operator.
In a column context, produces the clause a - b.
Abstract classes can override this to customize issubclass().
This is invoked early on by abc.ABCMeta.__subclasscheck__(). It should return True, False or NotImplemented. If it returns NotImplemented, the normal algorithm is used. Otherwise, it overrides the normal algorithm (and the outcome is cached).
Implement the // operator.
In a column context, produces the clause a / b.
list of weak references to the object (if defined)
Produce a between() clause against the parent object, given the lower and upper range.
Produce a collate() clause against the parent object, given the collation string.
Implement the ‘concat’ operator.
In a column context, produces the clause a || b, or uses the concat() operator on MySQL.
Implement the ‘contains’ operator.
In a column context, produces the clause LIKE '%<other>%'
Produce a distinct() clause against the parent object.
Implement the ‘endswith’ operator.
In a column context, produces the clause LIKE '%<other>'
Implement the ilike operator.
In a column context, produces the clause a ILIKE other.
E.g.:
select([sometable]).where(sometable.c.column.ilike("%foobar%"))
Parameters: |
---|
See also
Implement the in operator.
In a column context, produces the clause a IN other. “other” may be a tuple/list of column expressions, or a select() construct.
Implement the IS operator.
Normally, IS is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS may be desirable if comparing to boolean values on certain platforms.
New in version 0.7.9.
See also
Implement the IS NOT operator.
Normally, IS NOT is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS NOT may be desirable if comparing to boolean values on certain platforms.
New in version 0.7.9.
See also
Implement the like operator.
In a column context, produces the clause a LIKE other.
E.g.:
select([sometable]).where(sometable.c.column.like("%foobar%"))
Parameters: |
---|
See also
Implements the ‘match’ operator.
In a column context, this produces a MATCH clause, i.e. MATCH '<other>'. The allowed contents of other are database backend specific.
implement the NOT ILIKE operator.
This is equivalent to using negation with ColumnOperators.ilike(), i.e. ~x.ilike(y).
New in version 0.8.
See also
implement the NOT IN operator.
This is equivalent to using negation with ColumnOperators.in_(), i.e. ~x.in_(y).
New in version 0.8.
See also
implement the NOT LIKE operator.
This is equivalent to using negation with ColumnOperators.like(), i.e. ~x.like(y).
New in version 0.8.
See also
Produce a nullsfirst() clause against the parent object.
Produce a nullslast() clause against the parent object.
produce a generic operator function.
e.g.:
somecolumn.op("*")(5)
produces:
somecolumn * 5
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.
Parameters: |
|
---|
Operate on an argument.
This is the lowest level of operation, raises NotImplementedError by default.
Overriding this on a subclass can allow common behavior to be applied to all operations. For example, overriding ColumnOperators to apply func.lower() to the left and right side:
class MyComparator(ColumnOperators):
def operate(self, op, other):
return op(func.lower(self), func.lower(other))
Parameters: |
---|
Reverse operate on an argument.
Usage is the same as operate().
Implement the startwith operator.
In a column context, produces the clause LIKE '<other>%'
Hack, allows datetime objects to be compared on the LHS.
Bases: sqlalchemy.sql.expression.ColumnElement
Represent a SQL EXTRACT clause, extract(field FROM expr).
Bases: sqlalchemy.sql.expression.ColumnElement
Represent the false keyword, or equivalent, in a SQL statement.
Bases: sqlalchemy.sql.expression.ColumnElement
Represents a column label (AS).
Represent a label, as typically applied to any column-level element using the AS sql keyword.
Bases: sqlalchemy.sql.expression.ColumnElement
Represent the NULL keyword in a SQL statement.
Bases: sqlalchemy.sql.expression.ColumnElement
Represent an OVER clause.
This is a special operator against a so-called “window” function, as well as any aggregate function, which produces results relative to the result set itself. It’s supported only by certain database backends.
Bases: sqlalchemy.sql.expression.Executable, sqlalchemy.sql.expression.ClauseElement
Represent a literal SQL text fragment.
Public constructor is the text() function.
Establish the values and/or types of bound parameters within this TextClause construct.
Given a text construct such as:
from sqlalchemy import text
stmt = text("SELECT id, name FROM user WHERE name=:name "
"AND timestamp=:timestamp")
the TextClause.bindparams() method can be used to establish the initial value of :name and :timestamp, using simple keyword arguments:
stmt = stmt.bindparams(name='jack',
timestamp=datetime.datetime(2012, 10, 8, 15, 12, 5))
Where above, new BindParameter objects will be generated with the names name and timestamp, and values of jack and datetime.datetime(2012, 10, 8, 15, 12, 5), respectively. The types will be inferred from the values given, in this case String and DateTime.
When specific typing behavior is needed, the positional *binds argument can be used in which to specify bindparam() constructs directly. These constructs must include at least the key argument, then an optional value and type:
from sqlalchemy import bindparam
stmt = stmt.bindparams(
bindparam('name', value='jack', type_=String),
bindparam('timestamp', type_=DateTime)
)
Above, we specified the type of DateTime for the timestamp bind, and the type of String for the name bind. In the case of name we also set the default value of "jack".
Additional bound parameters can be supplied at statement execution time, e.g.:
result = connection.execute(stmt,
timestamp=datetime.datetime(2012, 10, 8, 15, 12, 5))
The TextClause.bindparams() method can be called repeatedly, where it will re-use existing BindParameter objects to add new information. For example, we can call TextClause.bindparams() first with typing information, and a second time with value information, and it will be combined:
stmt = text("SELECT id, name FROM user WHERE name=:name "
"AND timestamp=:timestamp")
stmt = stmt.bindparams(
bindparam('name', type_=String),
bindparam('timestamp', type_=DateTime)
)
stmt = stmt.bindparams(
name='jack',
timestamp=datetime.datetime(2012, 10, 8, 15, 12, 5)
)
New in version 0.9.0: The TextClause.bindparams() method supersedes the argument bindparams passed to text().
Turn this TextClause object into a TextAsFrom object that can be embedded into another statement.
This function essentially bridges the gap between an entirely textual SELECT statement and the SQL expression language concept of a “selectable”:
from sqlalchemy.sql import column, text
stmt = text("SELECT id, name FROM some_table")
stmt = stmt.columns(column('id'), column('name')).alias('st')
stmt = select([mytable]).\
select_from(
mytable.join(stmt, mytable.c.name == stmt.c.name)
).where(stmt.c.id > 5)
Above, we used untyped column() elements. These can also have types specified, which will impact how the column behaves in expressions as well as determining result set behavior:
stmt = text("SELECT id, name, timestamp FROM some_table")
stmt = stmt.columns(
column('id', Integer),
column('name', Unicode),
column('timestamp', DateTime)
)
for id, name, timestamp in connection.execute(stmt):
print(id, name, timestamp)
Keyword arguments allow just the names and types of columns to be specified, where the column() elements will be generated automatically:
stmt = text("SELECT id, name, timestamp FROM some_table")
stmt = stmt.columns(
id=Integer,
name=Unicode,
timestamp=DateTime
)
for id, name, timestamp in connection.execute(stmt):
print(id, name, timestamp)
The TextClause.columns() method provides a direct route to calling FromClause.alias() as well as SelectBase.cte() against a textual SELECT statement:
stmt = stmt.columns(id=Integer, name=String).cte('st')
stmt = select([sometable]).where(sometable.c.id == stmt.c.id)
New in version 0.9.0: text() can now be converted into a fully featured “selectable” construct using the TextClause.columns() method. This method supersedes the typemap argument to text().
Bases: sqlalchemy.sql.expression.ClauseList, sqlalchemy.sql.expression.ColumnElement
Represent a SQL tuple.
Bases: sqlalchemy.sql.expression.ColumnElement
Represent the true keyword, or equivalent, in a SQL statement.
Represent a ‘custom’ operator.
custom_op is normally instantitated when the ColumnOperators.op() method is used to create a custom operator callable. The class can also be used directly when programmatically constructing expressions. E.g. to represent the “factorial” operation:
from sqlalchemy.sql import UnaryExpression
from sqlalchemy.sql import operators
from sqlalchemy import Numeric
unary = UnaryExpression(table.c.somecolumn,
modifier=operators.custom_op("!"),
type_=Numeric)
Base of comparison and logical operators.
Implements base methods operate() and reverse_operate(), as well as __and__(), __or__(), __invert__().
Usually is used via its most common subclass ColumnOperators.
Implement the & operator.
When used with SQL expressions, results in an AND operation, equivalent to and_(), that is:
a & b
is equivalent to:
from sqlalchemy import and_
and_(a, b)
Care should be taken when using & regarding operator precedence; the & operator has the highest precedence. The operands should be enclosed in parenthesis if they contain further sub expressions:
(a == 2) & (b == 4)
Implement the ~ operator.
When used with SQL expressions, results in a NOT operation, equivalent to not_(), that is:
~a
is equivalent to:
from sqlalchemy import not_
not_(a)
Implement the | operator.
When used with SQL expressions, results in an OR operation, equivalent to or_(), that is:
a | b
is equivalent to:
from sqlalchemy import or_
or_(a, b)
Care should be taken when using | regarding operator precedence; the | operator has the highest precedence. The operands should be enclosed in parenthesis if they contain further sub expressions:
(a == 2) | (b == 4)
list of weak references to the object (if defined)
produce a generic operator function.
e.g.:
somecolumn.op("*")(5)
produces:
somecolumn * 5
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.
Parameters: |
|
---|
Operate on an argument.
This is the lowest level of operation, raises NotImplementedError by default.
Overriding this on a subclass can allow common behavior to be applied to all operations. For example, overriding ColumnOperators to apply func.lower() to the left and right side:
class MyComparator(ColumnOperators):
def operate(self, op, other):
return op(func.lower(self), func.lower(other))
Parameters: |
---|
Reverse operate on an argument.
Usage is the same as operate().
Bases: __builtin__.unicode
Represent a SQL identifier combined with quoting preferences.
quoted_name is a Python unicode/str subclass which represents a particular identifier name along with a quote flag. This quote flag, when set to True or False, overrides automatic quoting behavior for this identifier in order to either unconditionally quote or to not quote the name. If left at its default of None, quoting behavior is applied to the identifier on a per-backend basis based on an examination of the token itself.
A quoted_name object with quote=True is also prevented from being modified in the case of a so-called “name normalize” option. Certain database backends, such as Oracle, Firebird, and DB2 “normalize” case-insensitive names as uppercase. The SQLAlchemy dialects for these backends convert from SQLAlchemy’s lower-case-means-insensitive convention to the upper-case-means-insensitive conventions of those backends. The quote=True flag here will prevent this conversion from occurring to support an identifier that’s quoted as all lower case against such a backend.
The quoted_name object is normally created automatically when specifying the name for key schema constructs such as Table, Column, and others. The class can also be passed explicitly as the name to any function that receives a name which can be quoted. Such as to use the Engine.has_table() method with an unconditionally quoted name:
from sqlaclchemy import create_engine
from sqlalchemy.sql.elements import quoted_name
engine = create_engine("oracle+cx_oracle://some_dsn")
engine.has_table(quoted_name("some_table", True))
The above logic will run the “has table” logic against the Oracle backend, passing the name exactly as "some_table" without converting to upper case.
New in version 0.9.0.
Bases: sqlalchemy.sql.expression.ColumnElement
Define a ‘unary’ expression.
A unary expression has a single column expression and an operator. The operator can be placed on the left (where it is called the ‘operator’) or right (where it is called the ‘modifier’) of the column expression.
Compare this UnaryExpression against the given ClauseElement.