CHECK_CONSTRAINTS

The CHECK_CONSTRAINTS table provides information about CHECK constraints on tables.

USE INFORMATION_SCHEMA; DESC CHECK_CONSTRAINTS;

The output is as follows:

+--------------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------------+-------------+------+-----+---------+-------+ | CONSTRAINT_CATALOG | varchar(64) | NO | | NULL | | | CONSTRAINT_SCHEMA | varchar(64) | NO | | NULL | | | CONSTRAINT_NAME | varchar(64) | NO | | NULL | | | CHECK_CLAUSE | longtext | NO | | NULL | | +--------------------+-------------+------+-----+---------+-------+ 4 rows in set (0.00 sec)

The following example adds a CHECK constraint using the CREATE TABLE statement:

CREATE TABLE test.t1 (id INT PRIMARY KEY, CHECK (id%2 = 0)); SELECT * FROM CHECK_CONSTRAINTS\G

The output is as follows:

*************************** 1. row *************************** CONSTRAINT_CATALOG: def CONSTRAINT_SCHEMA: test CONSTRAINT_NAME: t1_chk_1 CHECK_CLAUSE: (`id` % 2 = 0) 1 row in set (0.00 sec)

Fields in the CHECK_CONSTRAINTS table are described as follows:

  • CONSTRAINT_CATALOG: The catalog of the constraint, which is always def.
  • CONSTRAINT_SCHEMA: The schema of the constraint.
  • CONSTRAINT_NAME: The name of the constraint.
  • CHECK_CLAUSE: The clause of the check constraint.