28.4.12 The INFORMATION_SCHEMA INNODB_FOREIGN Table

The INNODB_FOREIGN table provides metadata about InnoDB foreign keys.

For related usage information and examples, see Section 17.15.3, “InnoDB INFORMATION_SCHEMA Schema Object Tables”.

The INNODB_FOREIGN table has these columns:

• ID

  The name (not a numeric value) of the foreign key index, preceded by the schema (database) name (for example, test/products_fk).

• FOR_NAME

  The name of the child table in this foreign key relationship.

• REF_NAME

  The name of the parent table in this foreign key relationship.

• N_COLS

  The number of columns in the foreign key index.

• TYPE

  A collection of bit flags with information about the foreign key column, ORed together. 0 = ON DELETE/UPDATE RESTRICT, 1 = ON DELETE CASCADE, 2 = ON DELETE SET NULL, 4 = ON UPDATE CASCADE, 8 = ON UPDATE SET NULL, 16 = ON DELETE NO ACTION, 32 = ON UPDATE NO ACTION.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_FOREIGN\G
*************************** 1. row ***************************
      ID: test/fk1
FOR_NAME: test/child
REF_NAME: test/parent
  N_COLS: 1
    TYPE: 1

Notes

• You must have the PROCESS privilege to query this table.

• Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.