Customizing DDL
In the preceding sections we’ve discussed a variety of schema constructs including Table
, ForeignKeyConstraint
, CheckConstraint
, and Sequence
. Throughout, we’ve relied upon the create()
and create_all()
methods of Table
and MetaData
in order to issue data definition language (DDL) for all constructs. When issued, a pre-determined order of operations is invoked, and DDL to create each table is created unconditionally including all constraints and other objects associated with it. For more complex scenarios where database-specific DDL is required, SQLAlchemy offers two techniques which can be used to add any DDL based on any condition, either accompanying the standard generation of tables or by itself.
Custom DDL
Custom DDL phrases are most easily achieved using the DDL
construct. This construct works like all the other DDL elements except it accepts a string which is the text to be emitted:
event.listen(
metadata,
"after_create",
DDL("ALTER TABLE users ADD CONSTRAINT "
"cst_user_name_length "
" CHECK (length(user_name) >= 8)")
)
A more comprehensive method of creating libraries of DDL constructs is to use custom compilation - see Custom SQL Constructs and Compilation Extension for details.
Controlling DDL Sequences
The DDL
construct introduced previously also has the ability to be invoked conditionally based on inspection of the database. This feature is available using the DDLElement.execute_if()
method. For example, if we wanted to create a trigger but only on the PostgreSQL backend, we could invoke this as:
mytable = Table(
'mytable', metadata,
Column('id', Integer, primary_key=True),
Column('data', String(50))
)
func = DDL(
"CREATE FUNCTION my_func() "
"RETURNS TRIGGER AS $$ "
"BEGIN "
"NEW.data := 'ins'; "
"RETURN NEW; "
"END; $$ LANGUAGE PLPGSQL"
)
trigger = DDL(
"CREATE TRIGGER dt_ins BEFORE INSERT ON mytable "
"FOR EACH ROW EXECUTE PROCEDURE my_func();"
)
event.listen(
mytable,
'after_create',
func.execute_if(dialect='postgresql')
)
event.listen(
mytable,
'after_create',
trigger.execute_if(dialect='postgresql')
)
The DDLElement.execute_if.dialect
keyword also accepts a tuple of string dialect names:
event.listen(
mytable,
"after_create",
trigger.execute_if(dialect=('postgresql', 'mysql'))
)
event.listen(
mytable,
"before_drop",
trigger.execute_if(dialect=('postgresql', 'mysql'))
)
The DDLElement.execute_if()
method can also work against a callable function that will receive the database connection in use. In the example below, we use this to conditionally create a CHECK constraint, first looking within the PostgreSQL catalogs to see if it exists:
def should_create(ddl, target, connection, **kw):
row = connection.execute(
"select conname from pg_constraint where conname='%s'" %
ddl.element.name).scalar()
return not bool(row)
def should_drop(ddl, target, connection, **kw):
return not should_create(ddl, target, connection, **kw)
event.listen(
users,
"after_create",
DDL(
"ALTER TABLE users ADD CONSTRAINT "
"cst_user_name_length CHECK (length(user_name) >= 8)"
).execute_if(callable_=should_create)
)
event.listen(
users,
"before_drop",
DDL(
"ALTER TABLE users DROP CONSTRAINT cst_user_name_length"
).execute_if(callable_=should_drop)
)
sqlusers.create(engine)
CREATE TABLE users (
user_id SERIAL NOT NULL,
user_name VARCHAR(40) NOT NULL,
PRIMARY KEY (user_id)
)
select conname from pg_constraint where conname='cst_user_name_length'
ALTER TABLE users ADD CONSTRAINT cst_user_name_length CHECK (length(user_name) >= 8)
sqlusers.drop(engine)
select conname from pg_constraint where conname='cst_user_name_length'
ALTER TABLE users DROP CONSTRAINT cst_user_name_length
DROP TABLE users
Using the built-in DDLElement Classes
The sqlalchemy.schema
package contains SQL expression constructs that provide DDL expressions. For example, to produce a CREATE TABLE
statement:
from sqlalchemy.schema import CreateTable
with engine.connect() as conn:
sql conn.execute(CreateTable(mytable))
CREATE TABLE mytable (
col1 INTEGER,
col2 INTEGER,
col3 INTEGER,
col4 INTEGER,
col5 INTEGER,
col6 INTEGER
)
Above, the CreateTable
construct works like any other expression construct (such as select()
, table.insert()
, etc.). All of SQLAlchemy’s DDL oriented constructs are subclasses of the DDLElement
base class; this is the base of all the objects corresponding to CREATE and DROP as well as ALTER, not only in SQLAlchemy but in Alembic Migrations as well. A full reference of available constructs is in DDL Expression Constructs API.
User-defined DDL constructs may also be created as subclasses of DDLElement
itself. The documentation in Custom SQL Constructs and Compilation Extension has several examples of this.
The event-driven DDL system described in the previous section Controlling DDL Sequences is available with other DDLElement
objects as well. However, when dealing with the built-in constructs such as CreateIndex
, CreateSequence
, etc, the event system is of limited use, as methods like Table.create()
and MetaData.create_all()
will invoke these constructs unconditionally. In a future SQLAlchemy release, the DDL event system including conditional execution will taken into account for built-in constructs that currently invoke in all cases.
We can illustrate an event-driven example with the AddConstraint
and DropConstraint
constructs, as the event-driven system will work for CHECK and UNIQUE constraints, using these as we did in our previous example of DDLElement.execute_if()
:
def should_create(ddl, target, connection, **kw):
row = connection.execute(
"select conname from pg_constraint where conname='%s'" %
ddl.element.name).scalar()
return not bool(row)
def should_drop(ddl, target, connection, **kw):
return not should_create(ddl, target, connection, **kw)
event.listen(
users,
"after_create",
AddConstraint(constraint).execute_if(callable_=should_create)
)
event.listen(
users,
"before_drop",
DropConstraint(constraint).execute_if(callable_=should_drop)
)
sqlusers.create(engine)
CREATE TABLE users (
user_id SERIAL NOT NULL,
user_name VARCHAR(40) NOT NULL,
PRIMARY KEY (user_id)
)
select conname from pg_constraint where conname='cst_user_name_length'
ALTER TABLE users ADD CONSTRAINT cst_user_name_length CHECK (length(user_name) >= 8)
sqlusers.drop(engine)
select conname from pg_constraint where conname='cst_user_name_length'
ALTER TABLE users DROP CONSTRAINT cst_user_name_length
DROP TABLE users
While the above example is against the built-in AddConstraint
and DropConstraint
objects, the main usefulness of DDL events for now remains focused on the use of the DDL
construct itself, as well as with user-defined subclasses of DDLElement
that aren’t already part of the MetaData.create_all()
, Table.create()
, and corresponding “drop” processes.
DDL Expression Constructs API
Object Name | Description |
---|---|
Base class for DDL constructs that represent CREATE and DROP or equivalents. | |
Represent an ALTER TABLE ADD CONSTRAINT statement. | |
Represent a | |
Represent a CREATE INDEX statement. | |
Represent a CREATE SCHEMA statement. | |
Represent a CREATE SEQUENCE statement. | |
Represent a CREATE TABLE statement. | |
A literal DDL statement. | |
Base class for DDL expression constructs. | |
Represent an ALTER TABLE DROP CONSTRAINT statement. | |
Represent a DROP INDEX statement. | |
Represent a DROP SCHEMA statement. | |
Represent a DROP SEQUENCE statement. | |
Represent a DROP TABLE statement. | |
| Sort a collection of |
| Sort a collection of |
function sqlalchemy.schema.``sort_tables
(tables, skip_fn=None, extra_dependencies=None)
Sort a collection of Table
objects based on dependency.
This is a dependency-ordered sort which will emit Table
objects such that they will follow their dependent Table
objects. Tables are dependent on another based on the presence of ForeignKeyConstraint
objects as well as explicit dependencies added by Table.add_is_dependent_on()
.
Warning
The sort_tables()
function cannot by itself accommodate automatic resolution of dependency cycles between tables, which are usually caused by mutually dependent foreign key constraints. When these cycles are detected, the foreign keys of these tables are omitted from consideration in the sort. A warning is emitted when this condition occurs, which will be an exception raise in a future release. Tables which are not part of the cycle will still be returned in dependency order.
To resolve these cycles, the ForeignKeyConstraint.use_alter
parameter may be applied to those constraints which create a cycle. Alternatively, the sort_tables_and_constraints()
function will automatically return foreign key constraints in a separate collection when cycles are detected so that they may be applied to a schema separately.
Changed in version 1.3.17: - a warning is emitted when sort_tables()
cannot perform a proper sort due to cyclical dependencies. This will be an exception in a future release. Additionally, the sort will continue to return other tables not involved in the cycle in dependency order which was not the case previously.
Parameters
tables – a sequence of
Table
objects.skip_fn – optional callable which will be passed a
ForeignKey
object; if it returns True, this constraint will not be considered as a dependency. Note this is different from the same parameter insort_tables_and_constraints()
, which is instead passed the owningForeignKeyConstraint
object.extra_dependencies – a sequence of 2-tuples of tables which will also be considered as dependent on each other.
See also
MetaData.sorted_tables
- uses this function to sort
function sqlalchemy.schema.``sort_tables_and_constraints
(tables, filter_fn=None, extra_dependencies=None, _warn_for_cycles=False)
Sort a collection of Table
/ ForeignKeyConstraint
objects.
This is a dependency-ordered sort which will emit tuples of (Table, [ForeignKeyConstraint, ...])
such that each Table
follows its dependent Table
objects. Remaining ForeignKeyConstraint
objects that are separate due to dependency rules not satisfied by the sort are emitted afterwards as (None, [ForeignKeyConstraint ...])
.
Tables are dependent on another based on the presence of ForeignKeyConstraint
objects, explicit dependencies added by Table.add_is_dependent_on()
, as well as dependencies stated here using the sort_tables_and_constraints.skip_fn
and/or sort_tables_and_constraints.extra_dependencies
parameters.
Parameters
tables – a sequence of
Table
objects.filter_fn – optional callable which will be passed a
ForeignKeyConstraint
object, and returns a value based on whether this constraint should definitely be included or excluded as an inline constraint, or neither. If it returns False, the constraint will definitely be included as a dependency that cannot be subject to ALTER; if True, it will only be included as an ALTER result at the end. Returning None means the constraint is included in the table-based result unless it is detected as part of a dependency cycle.extra_dependencies – a sequence of 2-tuples of tables which will also be considered as dependent on each other.
New in version 1.0.0.
See also
class sqlalchemy.schema.``DDLElement
Base class for DDL expression constructs.
This class is the base for the general purpose DDL
class, as well as the various create/drop clause constructs such as CreateTable
, DropTable
, AddConstraint
, etc.
DDLElement
integrates closely with SQLAlchemy events, introduced in Events. An instance of one is itself an event receiving callable:
event.listen(
users,
'after_create',
AddConstraint(constraint).execute_if(dialect='postgresql')
)
See also
Class signature
class sqlalchemy.schema.DDLElement
(sqlalchemy.sql.roles.DDLRole
, sqlalchemy.sql.expression.Executable
, sqlalchemy.schema._DDLCompiles
)
method
sqlalchemy.schema.DDLElement.
__call__
(target, bind, \*kw*)Execute the DDL as a ddl_listener.
method
sqlalchemy.schema.DDLElement.
against
(target)Return a copy of this
DDLElement
which will include the given target.This essentially applies the given item to the
.target
attribute of the returnedDDLElement
object. This target is then usable by event handlers and compilation routines in order to provide services such as tokenization of a DDL string in terms of a particularTable
.When a
DDLElement
object is established as an event handler for theDDLEvents.before_create()
orDDLEvents.after_create()
events, and the event then occurs for a given target such as aConstraint
orTable
, that target is established with a copy of theDDLElement
object using this method, which then proceeds to theDDLElement.execute()
method in order to invoke the actual DDL instruction.Parameters
target – a
SchemaItem
that will be the subject of a DDL operation.Returns
a copy of this
DDLElement
with the.target
attribute assigned to the givenSchemaItem
.
See also
DDL
- uses tokenization against the “target” when processing the DDL string.attribute
sqlalchemy.schema.DDLElement.
bind
attribute
sqlalchemy.schema.DDLElement.
callable_
= Noneattribute
sqlalchemy.schema.DDLElement.
dialect
= Nonemethod
sqlalchemy.schema.DDLElement.
execute
(bind=None, target=None)Execute this DDL immediately.
Deprecated since version 1.4: The
DDLElement.execute()
method is considered legacy as of the 1.x series of SQLAlchemy and will be removed in 2.0. All statement execution in SQLAlchemy 2.0 is performed by theConnection.execute()
method ofConnection
, or in the ORM by theSession.execute()
method ofSession
. (Background on SQLAlchemy 2.0 at: Migrating to SQLAlchemy 2.0)Executes the DDL statement in isolation using the supplied
Connectable
orConnectable
assigned to the.bind
property, if not supplied. If the DDL has a conditionalon
criteria, it will be invoked with None as the event.Parameters
bind – Optional, an
Engine
orConnection
. If not supplied, a validConnectable
must be present in the.bind
property.target – Optional, defaults to None. The target
SchemaItem
for the execute call. This is equivalent to passing theSchemaItem
to theDDLElement.against()
method and then invokingDDLElement.execute()
upon the resultingDDLElement
object. SeeDDLElement.against()
for further detail.
method
sqlalchemy.schema.DDLElement.
execute_if
(dialect=None, callable_=None, state=None)Return a callable that will execute this
DDLElement
conditionally within an event handler.Used to provide a wrapper for event listening:
event.listen(
metadata,
'before_create',
DDL("my_ddl").execute_if(dialect='postgresql')
)
Parameters
dialect –
May be a string, tuple or a callable predicate. If a string, it will be compared to the name of the executing database dialect:
DDL('something').execute_if(dialect='postgresql')
If a tuple, specifies multiple dialect names:
DDL('something').execute_if(dialect=('postgresql', 'mysql'))
callable_ –
A callable, which will be invoked with four positional arguments as well as optional keyword arguments:
ddl
This DDL element.
target
The
Table
orMetaData
object which is the target of this event. May be None if the DDL is executed explicitly.bind
The
Connection
being used for DDL executiontables
Optional keyword argument - a list of Table objects which are to be created/ dropped within a MetaData.create_all() or drop_all() method call.
state
Optional keyword argument - will be the
state
argument passed to this function.checkfirst
Keyword argument, will be True if the ‘checkfirst’ flag was set during the call to
create()
,create_all()
,drop()
,drop_all()
.If the callable returns a True value, the DDL statement will be executed.
state – any value which will be passed to the callable_ as the
state
keyword argument.
See also
[`DDLEvents`]($db915629bc58de5f.md#sqlalchemy.events.DDLEvents "sqlalchemy.events.DDLEvents")
[Events]($c14d75f7aa5f8339.md)
attribute
sqlalchemy.schema.DDLElement.
on
= Noneattribute
sqlalchemy.schema.DDLElement.
target
= None
class sqlalchemy.schema.``DDL
(statement, context=None, bind=None)
A literal DDL statement.
Specifies literal SQL DDL to be executed by the database. DDL objects function as DDL event listeners, and can be subscribed to those events listed in DDLEvents
, using either Table
or MetaData
objects as targets. Basic templating support allows a single DDL instance to handle repetitive tasks for multiple tables.
Examples:
from sqlalchemy import event, DDL
tbl = Table('users', metadata, Column('uid', Integer))
event.listen(tbl, 'before_create', DDL('DROP TRIGGER users_trigger'))
spow = DDL('ALTER TABLE %(table)s SET secretpowers TRUE')
event.listen(tbl, 'after_create', spow.execute_if(dialect='somedb'))
drop_spow = DDL('ALTER TABLE users SET secretpowers FALSE')
connection.execute(drop_spow)
When operating on Table events, the following statement
string substitutions are available:
%(table)s - the Table name, with any required quoting applied
%(schema)s - the schema name, with any required quoting applied
%(fullname)s - the Table name including schema, quoted if needed
The DDL’s “context”, if any, will be combined with the standard substitutions noted above. Keys present in the context will override the standard substitutions.
Class signature
class sqlalchemy.schema.DDL
(sqlalchemy.schema.DDLElement
)
method
sqlalchemy.schema.DDL.
__init__
(statement, context=None, bind=None)Create a DDL statement.
Parameters
statement –
A string or unicode string to be executed. Statements will be processed with Python’s string formatting operator. See the
context
argument and theexecute_at
method.A literal ‘%’ in a statement must be escaped as ‘%%’.
SQL bind parameters are not available in DDL statements.
context – Optional dictionary, defaults to None. These values will be available for use in string substitutions on the DDL statement.
bind –
Optional. A
Connectable
, used by default whenexecute()
is invoked without a bind argument.Deprecated since version 1.4: The
DDL.bind
argument is deprecated and will be removed in SQLAlchemy 2.0.
See also
[`DDLEvents`]($db915629bc58de5f.md#sqlalchemy.events.DDLEvents "sqlalchemy.events.DDLEvents")
[Events]($c14d75f7aa5f8339.md)
class sqlalchemy.schema.``_CreateDropBase
(element, bind=None, if_exists=False, if_not_exists=False, _legacy_bind=None)
Base class for DDL constructs that represent CREATE and DROP or equivalents.
The common theme of _CreateDropBase is a single element
attribute which refers to the element to be created or dropped.
Class signature
class sqlalchemy.schema._CreateDropBase
(sqlalchemy.schema.DDLElement
)
class sqlalchemy.schema.``CreateTable
(element, bind=None, include_foreign_key_constraints=None, if_not_exists=False)
Represent a CREATE TABLE statement.
Class signature
class sqlalchemy.schema.CreateTable
(sqlalchemy.schema._CreateDropBase
)
method
sqlalchemy.schema.CreateTable.
__init__
(element, bind=None, include_foreign_key_constraints=None, if_not_exists=False)Create a
CreateTable
construct.
Deprecated since version 1.4: The [`CreateTable.bind`](#sqlalchemy.schema.CreateTable.params.bind "sqlalchemy.schema.CreateTable") argument is deprecated and will be removed in SQLAlchemy 2.0.
- Parameters
- **include\_foreign\_key\_constraints** –
optional sequence of [`ForeignKeyConstraint`]($dac8da0dbad15694.md#sqlalchemy.schema.ForeignKeyConstraint "sqlalchemy.schema.ForeignKeyConstraint") objects that will be included inline within the CREATE construct; if omitted, all foreign key constraints that do not specify use\_alter=True are included.
New in version 1.0.0.
- **if\_not\_exists** –
if True, an IF NOT EXISTS operator will be applied to the construct.
New in version 1.4.0b2.
class sqlalchemy.schema.``DropTable
(element, bind=None, if_exists=False)
Represent a DROP TABLE statement.
Class signature
class sqlalchemy.schema.DropTable
(sqlalchemy.schema._CreateDropBase
)
method
sqlalchemy.schema.DropTable.
__init__
(element, bind=None, if_exists=False)Create a
DropTable
construct.
Deprecated since version 1.4: The [`DropTable.bind`](#sqlalchemy.schema.DropTable.params.bind "sqlalchemy.schema.DropTable") argument is deprecated and will be removed in SQLAlchemy 2.0.
- Parameters
**if\_exists** –
if True, an IF EXISTS operator will be applied to the construct.
New in version 1.4.0b2.
class sqlalchemy.schema.``CreateColumn
(element)
Represent a Column
as rendered in a CREATE TABLE statement, via the CreateTable
construct.
This is provided to support custom column DDL within the generation of CREATE TABLE statements, by using the compiler extension documented in Custom SQL Constructs and Compilation Extension to extend CreateColumn
.
Typical integration is to examine the incoming Column
object, and to redirect compilation if a particular flag or condition is found:
from sqlalchemy import schema
from sqlalchemy.ext.compiler import compiles
@compiles(schema.CreateColumn)
def compile(element, compiler, **kw):
column = element.element
if "special" not in column.info:
return compiler.visit_create_column(element, **kw)
text = "%s SPECIAL DIRECTIVE %s" % (
column.name,
compiler.type_compiler.process(column.type)
)
default = compiler.get_column_default_string(column)
if default is not None:
text += " DEFAULT " + default
if not column.nullable:
text += " NOT NULL"
if column.constraints:
text += " ".join(
compiler.process(const)
for const in column.constraints)
return text
The above construct can be applied to a Table
as follows:
from sqlalchemy import Table, Metadata, Column, Integer, String
from sqlalchemy import schema
metadata = MetaData()
table = Table('mytable', MetaData(),
Column('x', Integer, info={"special":True}, primary_key=True),
Column('y', String(50)),
Column('z', String(20), info={"special":True})
)
metadata.create_all(conn)
Above, the directives we’ve added to the Column.info
collection will be detected by our custom compilation scheme:
CREATE TABLE mytable (
x SPECIAL DIRECTIVE INTEGER NOT NULL,
y VARCHAR(50),
z SPECIAL DIRECTIVE VARCHAR(20),
PRIMARY KEY (x)
)
The CreateColumn
construct can also be used to skip certain columns when producing a CREATE TABLE
. This is accomplished by creating a compilation rule that conditionally returns None
. This is essentially how to produce the same effect as using the system=True
argument on Column
, which marks a column as an implicitly-present “system” column.
For example, suppose we wish to produce a Table
which skips rendering of the PostgreSQL xmin
column against the PostgreSQL backend, but on other backends does render it, in anticipation of a triggered rule. A conditional compilation rule could skip this name only on PostgreSQL:
from sqlalchemy.schema import CreateColumn
@compiles(CreateColumn, "postgresql")
def skip_xmin(element, compiler, **kw):
if element.element.name == 'xmin':
return None
else:
return compiler.visit_create_column(element, **kw)
my_table = Table('mytable', metadata,
Column('id', Integer, primary_key=True),
Column('xmin', Integer)
)
Above, a CreateTable
construct will generate a CREATE TABLE
which only includes the id
column in the string; the xmin
column will be omitted, but only against the PostgreSQL backend.
Class signature
class sqlalchemy.schema.CreateColumn
(sqlalchemy.schema._DDLCompiles
)
class sqlalchemy.schema.``CreateSequence
(element, bind=None, if_exists=False, if_not_exists=False, _legacy_bind=None)
Represent a CREATE SEQUENCE statement.
Class signature
class sqlalchemy.schema.CreateSequence
(sqlalchemy.schema._CreateDropBase
)
class sqlalchemy.schema.``DropSequence
(element, bind=None, if_exists=False, if_not_exists=False, _legacy_bind=None)
Represent a DROP SEQUENCE statement.
Class signature
class sqlalchemy.schema.DropSequence
(sqlalchemy.schema._CreateDropBase
)
class sqlalchemy.schema.``CreateIndex
(element, bind=None, if_not_exists=False)
Represent a CREATE INDEX statement.
Class signature
class sqlalchemy.schema.CreateIndex
(sqlalchemy.schema._CreateDropBase
)
method
sqlalchemy.schema.CreateIndex.
__init__
(element, bind=None, if_not_exists=False)Create a
Createindex
construct.
Deprecated since version 1.4: The [`CreateIndex.bind`](#sqlalchemy.schema.CreateIndex.params.bind "sqlalchemy.schema.CreateIndex") argument is deprecated and will be removed in SQLAlchemy 2.0.
- Parameters
**if\_not\_exists** –
if True, an IF NOT EXISTS operator will be applied to the construct.
New in version 1.4.0b2.
class sqlalchemy.schema.``DropIndex
(element, bind=None, if_exists=False)
Represent a DROP INDEX statement.
Class signature
class sqlalchemy.schema.DropIndex
(sqlalchemy.schema._CreateDropBase
)
method
sqlalchemy.schema.DropIndex.
__init__
(element, bind=None, if_exists=False)Create a
DropIndex
construct.
Deprecated since version 1.4: The [`DropIndex.bind`](#sqlalchemy.schema.DropIndex.params.bind "sqlalchemy.schema.DropIndex") argument is deprecated and will be removed in SQLAlchemy 2.0.
- Parameters
**if\_exists** –
if True, an IF EXISTS operator will be applied to the construct.
New in version 1.4.0b2.
class sqlalchemy.schema.``AddConstraint
(element, \args, **kw*)
Represent an ALTER TABLE ADD CONSTRAINT statement.
Class signature
class sqlalchemy.schema.AddConstraint
(sqlalchemy.schema._CreateDropBase
)
class sqlalchemy.schema.``DropConstraint
(element, cascade=False, \*kw*)
Represent an ALTER TABLE DROP CONSTRAINT statement.
Class signature
class sqlalchemy.schema.DropConstraint
(sqlalchemy.schema._CreateDropBase
)
class sqlalchemy.schema.``CreateSchema
(name, quote=None, \*kw*)
Represent a CREATE SCHEMA statement.
The argument here is the string name of the schema.
Class signature
class sqlalchemy.schema.CreateSchema
(sqlalchemy.schema._CreateDropBase
)
method
sqlalchemy.schema.CreateSchema.
__init__
(name, quote=None, \*kw*)Create a new
CreateSchema
construct.
class sqlalchemy.schema.``DropSchema
(name, quote=None, cascade=False, \*kw*)
Represent a DROP SCHEMA statement.
The argument here is the string name of the schema.
Class signature
class sqlalchemy.schema.DropSchema
(sqlalchemy.schema._CreateDropBase
)
method
sqlalchemy.schema.DropSchema.
__init__
(name, quote=None, cascade=False, \*kw*)Create a new
DropSchema
construct.