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  6. ALTER FOREIGN TABLE (For HDFS or OBS)

ALTER FOREIGN TABLE (For HDFS or OBS)

Function

ALTER FOREIGN TABLE (For HDFS or OBS) modifies an HDFS or OBS foreign table.

Precautions

None

Syntax

  • Set the attributes of the foreign table.
    ALTER FOREIGN TABLE [ IF EXISTS ]  table_name
        OPTIONS ( [ ADD | SET | DROP ] option ['value'] [, ... ]);
  • Set the owner of the foreign table.
    ALTER FOREIGN TABLE [ IF EXISTS ] tablename 
        OWNER TO new_owner;
  • Change the column of the foreign table.
    ALTER FOREIGN TABLE [ IF EXISTS ] tablename 
        action [, ... ];
    The action syntax is as follows:
    ALTER [ COLUMN ] column_name [ SET DATA ] TYPE data_type
       | ALTER [ COLUMN ] column_name { SET | DROP } NOT NULL
       | ALTER [ COLUMN ] column_name SET STATISTICS [PERCENT] integer
       | ALTER [ COLUMN ] column_name OPTIONS ( {[ ADD | SET | DROP ] option ['value'] } [, ... ])

    For details, see ALTER TABLE.

  • Add a foreign table informational constraint.
    ALTER FOREIGN TABLE [ IF EXISTS ] tablename
        ADD [ CONSTRAINT constraint_name ]
        { PRIMARY KEY | UNIQUE } ( column_name )
        [ NOT ENFORCED [ ENABLE QUERY OPTIMIZATION | DISABLE QUERY OPTIMIZATION ] | ENFORCED ];

    For parameters about adding foreign table informational constraints, see Parameter Description in CREATE FOREIGN TABLE (For HDFS or OBS).

  • Remove a foreign table informational constraint.
    ALTER FOREIGN TABLE [ IF EXISTS ] tablename 
        DROP CONSTRAINT constraint_name ;

Parameter Description

  • IF EXISTS

    Sends a notification instead of an error if no tables have identical names. The notification prompts that the table you are querying does not exist.

  • tablename

    Specifies the name of an existing foreign table to alter.

    Value range: An existing foreign table name.

  • new_owner

    Specifies the new owner of the foreign table.

    Value range: A string. It must be a valid user name.

  • data_type

    Specifies the new data type for an existing column.

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

  • constraint_name

    Specifies the name of an existing constraint to add or delete.

  • column_name

    Specifies the name of an existing column.

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

For details on how to modify other parameters in the foreign table, such as IF EXISTS, see Parameter Description in ALTER TABLE.

Example

See Example in CREATE FOREIGN TABLE (For HDFS or OBS).