28.4.12 INFORMATION_SCHEMA INNODB_FOREIGN 表
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
.
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
-
You must have the
PROCESS
privilege to query this table. -
Use the
INFORMATION_SCHEMA
COLUMNS
table or theSHOW COLUMNS
statement to view additional information about the columns of this table, including data types and default values.