CREATE FOREIGN TABLE7SQL - Language StatementsCREATE FOREIGN TABLEdefine a new foreign tableCREATE FOREIGN TABLE
CREATE FOREIGN TABLE [ IF NOT EXISTS ] table_name ( [
column_namedata_type [ OPTIONS ( option 'value' [, ... ] ) ] [ COLLATE collation ] [ column_constraint [ ... ] ]
[, ... ]
] )
SERVER server_name
[ OPTIONS ( option 'value' [, ... ] ) ]
where column_constraint is:
[ CONSTRAINT constraint_name ]
{ NOT NULL |
NULL |
DEFAULT default_expr }
DescriptionCREATE FOREIGN TABLE creates a new foreign table
in the current database. The table will be owned by the user issuing the
command.
If a schema name is given (for example, CREATE FOREIGN TABLE
myschema.mytable ...>) then the table is created in the specified
schema. Otherwise it is created in the current schema.
The name of the foreign table must be
distinct from the name of any other foreign table, table, sequence, index,
or view in the same schema.
CREATE FOREIGN TABLE also automatically creates a data
type that represents the composite type corresponding to one row of
the foreign table. Therefore, foreign tables cannot have the same
name as any existing data type in the same schema.
To be able to create a foreign table, you must have USAGE
privilege on the foreign server, as well as USAGE
privilege on all column types used in the table.
ParametersIF NOT EXISTS>
Do not throw an error if a relation with the same name already exists.
A notice is issued in this case. Note that there is no guarantee that
the existing relation is anything like the one that would have been
created.
table_name
The name (optionally schema-qualified) of the table to be created.
column_name
The name of a column to be created in the new table.
data_type
The data type of the column. This can include array
specifiers. For more information on the data types supported by
PostgreSQL, refer to .
NOT NULL>
The column is not allowed to contain null values.
NULL>
The column is allowed to contain null values. This is the default.
This clause is only provided for compatibility with
non-standard SQL databases. Its use is discouraged in new
applications.
DEFAULT
default_expr
The DEFAULT> clause assigns a default data value for
the column whose column definition it appears within. The value
is any variable-free expression (subqueries and cross-references
to other columns in the current table are not allowed). The
data type of the default expression must match the data type of the
column.
The default expression will be used in any insert operation that
does not specify a value for the column. If there is no default
for a column, then the default is null.
server_name
The name of an existing foreign server to use for the foreign table.
For details on defining a server, see .
OPTIONS ( option 'value' [, ...] )
Options to be associated with the new foreign table or one of its
columns.
The allowed option names and values are specific to each foreign
data wrapper and are validated using the foreign-data wrapper's
validator function. Duplicate option names are not allowed (although
it's OK for a table option and a column option to have the same name).
Examples
Create foreign table films>, which will be accessed through
the server film_server>:
CREATE FOREIGN TABLE films (
code char(5) NOT NULL,
title varchar(40) NOT NULL,
did integer NOT NULL,
date_prod date,
kind varchar(10),
len interval hour to minute
)
SERVER film_server;
Compatibility
The CREATE FOREIGN TABLE command largely conforms to the
SQL standard; however, much as with
CREATE TABLE>,
NULL> constraints and zero-column foreign tables are permitted.
The ability to specify a default value is also a PostgreSQL>
extension.
See Also