CREATE FOREIGN TABLE
Synopsis
CREATE FOREIGN TABLE [ IF NOT EXISTS ] table_name ( [
column_name data_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 }
Description
CREATE 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, view, or materialized 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.
Parameters
- IF 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 Глава 8.
- 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 CREATE SERVER.
- 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.