CREATE FOREIGN TABLE

Function

CREATE FOREIGN TABLE creates a foreign table.

Precautions

• System columns (such as tableoid and ctid) cannot be used in foreign tables. Among them, the appearance of Private and Shares mode requires the initial user and operation and maintenance administrator authority in operation mode (operation_mode).

Syntax

CreateForeignTable ::= CREATE FOREIGN TABLE [ IF NOT EXISTS ] table_name ( [
    column_name type_name [ OPTIONS ( option 'value') ] [ COLLATE collation ] [ column_constraint [ ... ] ]
    [, ... ]
] )
  SERVER server_name
[ OPTIONS ( option 'value' ) ]

The column_constraint can be:

column_constraint ::= [ CONSTRAINT constraint_name ]
{ NOT NULL |
  NULL |
  DEFAULT default_expr }

Parameter Description

• IF NOT EXISTS

  Sends a notice, but does not throw an error, if a table with the same name exists.

• table_name

  Specifies the name of a foreign table.

  Value range: a string. It must comply with the naming convention.

• column_name

  Specifies the name of a column in the foreign table.

  Value range: a string. It must comply with the naming convention.

• type_name

  Specifies the data type of the column.

• SERVER server_name

  Specifies the server name of the foreign table. The default value is mot_server.

  If you need to create an external table of Oracle, MySQL, PostgreSQL, or File type, you need to create the corresponding server manually first, see CREATE SERVER for the statement of creating server. Here the server_name should be the same as the server_name defined in the create server statement.

• OPTIONS ( option 'value' [, … ] )

  Options are related to the new foreign table or the columns in the foreign table. The allowed option names and values are specified by each foreign data wrapper, and are also verified by the verification function of the foreign data wrapper. The option name must be unique (although table options and table column options can share the same name).

  • Options supported by oracle_fdw are as follows:

    • table

      Name of a table on the Oracle server. The value must be the same as the table name recorded in the Oracle system catalog. Generally, the value consists of uppercase letters.

    • schema

      Schema (or owner) corresponding to the table. The value must be the same as the table name recorded in the Oracle system catalog. Generally, the value consists of uppercase letters.

  • Options supported by mysql_fdw are as follows:

    • dbname

      Name of the MySQL database.

    • table_name

      Name of a table in the MySQL database.

  • Options supported by postgres_fdw are as follows:

    • schema_name

      Schema name of a remote server. If this option is not specified, the schema name of the foreign table is used as the schema name of the remote server.

    • table_name

      Table name of a remote server. If this option is not specified, the name of the foreign table is used as the table name of the remote server.

    • column_name

      Column name of a table on a remote server. If this option is not specified, the column name of the foreign table is used as the column name of a table on a remote server.

  • Options supported by file_fdw are as follows:

    • filename

      File to be read. This parameter is mandatory and must be an absolute path.

    • format

      File format of the remote server, which is the same as the FORMAT option in the COPY statement. The value can be text, csv, binary, or fixed.

    • header

      Specifies whether a specified file has a header, which is the same as the HEADER option of the COPY statement.

    • delimiter

      File delimiter, which is the same as the DELIMITER option of the COPY statement.

    • quote

      Quote character of a file, which is the same as the QUOTE option of the COPY statement.

    • escape

      Escape character of a file, which is the same as the ESCAPE option of the COPY statement.

    • null

      Null string of a file, which is the same as the NULL option of the COPY statement.

    • encoding

      Encoding of a file, which is the same as the ENCODING option of the COPY statement.

    • force_not_null

      This is a Boolean option. If it is true, the value of the declared field cannot be an empty string. This option is the same as the FORCE_NOT_NULL option of the COPY statement.

NOTE: For details, please see file_fdw, oracle_fdw, mysql_fdw, postgres_fdw.

Helpful Links

ALTER FOREIGN TABLE and DROP FOREIGN TABLE