CHECK_CONSTRAINTS

CHECK_CONSTRAINTS 表提供关于表上 CHECK 约束的信息。

USE INFORMATION_SCHEMA; DESC CHECK_CONSTRAINTS;

命令输出如下:

+--------------------+-------------+------+-----+---------+-------+ | 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)

下述示例使用 CREATE TABLE 语句添加 CHECK 约束:

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

命令输出如下:

*************************** 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)

CHECK_CONSTRAINTS 表的字段描述如下:

  • CONSTRAINT_CATALOG:约束的目录,始终为 def
  • CONSTRAINT_SCHEMA:约束的库名。
  • CONSTRAINT_NAME:约束的名字。
  • CHECK_CLAUSE:检查约束的子句。
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