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CREATE FOREIGN TABLE(7) PostgreSQL 9.5.10 DocumentationCREATE FOREIGN TABLE(7)




NAME

       CREATE_FOREIGN_TABLE - define a new foreign table


SYNOPSIS

       CREATE FOREIGN TABLE [ IF NOT EXISTS ] table_name ( [
         { column_name data_type [ OPTIONS ( option 'value' [, ... ] ) ] [ COLLATE collation ] [ column_constraint [ ... ] ]
           | table_constraint }
           [, ... ]
       ] )
       [ INHERITS ( parent_table [, ... ] ) ]
         SERVER server_name
       [ OPTIONS ( option 'value' [, ... ] ) ]

       where column_constraint is:

       [ CONSTRAINT constraint_name ]
       { NOT NULL |
         NULL |
         CHECK ( expression ) [ NO INHERIT ] |
         DEFAULT default_expr }

       and table_constraint is:

       [ CONSTRAINT constraint_name ]
       CHECK ( expression ) [ NO INHERIT ]


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 Chapter 8, Data Types, in the documentation.

       COLLATE collation
           The COLLATE clause assigns a collation to the column (which must be
           of a collatable data type). If not specified, the column data
           type's default collation is used.

       INHERITS ( parent_table [, ... ] )
           The optional INHERITS clause specifies a list of tables from which
           the new foreign table automatically inherits all columns. Parent
           tables can be plain tables or foreign tables. See the similar form
           of CREATE TABLE (CREATE_TABLE(7)) for more details.

       CONSTRAINT constraint_name
           An optional name for a column or table constraint. If the
           constraint is violated, the constraint name is present in error
           messages, so constraint names like col must be positive can be used
           to communicate helpful constraint information to client
           applications. (Double-quotes are needed to specify constraint names
           that contain spaces.) If a constraint name is not specified, the
           system generates a name.

       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.

       CHECK ( expression ) [ NO INHERIT ]
           The CHECK clause specifies an expression producing a Boolean result
           which each row in the foreign table is expected to satisfy; that
           is, the expression should produce TRUE or UNKNOWN, never FALSE, for
           all rows in the foreign table. A check constraint specified as a
           column constraint should reference that column's value only, while
           an expression appearing in a table constraint can reference
           multiple columns.

           Currently, CHECK expressions cannot contain subqueries nor refer to
           variables other than columns of the current row. The system column
           tableoid may be referenced, but not any other system column.

           A constraint marked with NO INHERIT will not propagate to child
           tables.

       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
           (CREATE_SERVER(7)).

       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).


NOTES

       Constraints on foreign tables (such as CHECK or NOT NULL clauses) are
       not enforced by the core PostgreSQL system, and most foreign data
       wrappers do not attempt to enforce them either; that is, the constraint
       is simply assumed to hold true. There would be little point in such
       enforcement since it would only apply to rows inserted or updated via
       the foreign table, and not to rows modified by other means, such as
       directly on the remote server. Instead, a constraint attached to a
       foreign table should represent a constraint that is being enforced by
       the remote server.

       Some special-purpose foreign data wrappers might be the only access
       mechanism for the data they access, and in that case it might be
       appropriate for the foreign data wrapper itself to perform constraint
       enforcement. But you should not assume that a wrapper does that unless
       its documentation says so.

       Although PostgreSQL does not attempt to enforce constraints on foreign
       tables, it does assume that they are correct for purposes of query
       optimization. If there are rows visible in the foreign table that do
       not satisfy a declared constraint, queries on the table might produce
       incorrect answers. It is the user's responsibility to ensure that the
       constraint definition matches reality.


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 column default
       values is also a PostgreSQL extension. Table inheritance, in the form
       defined by PostgreSQL, is nonstandard.


SEE ALSO

       ALTER FOREIGN TABLE (ALTER_FOREIGN_TABLE(7)), DROP FOREIGN TABLE
       (DROP_FOREIGN_TABLE(7)), CREATE TABLE (CREATE_TABLE(7)), CREATE SERVER
       (CREATE_SERVER(7)), IMPORT FOREIGN SCHEMA (IMPORT_FOREIGN_SCHEMA(7))



PostgreSQL 9.5.10                    2017              CREATE FOREIGN TABLE(7)

PostgreSQL 9.5.10 - Generated Thu Nov 30 16:50:26 CST 2017
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