mysql - 使用特定外键选项查询所有约束

Question

我在 MySql 中有几个带有外键的表。例如:

CREATE TABLE rooms (
  room_no int(11) NOT NULL AUTO_INCREMENT,
  room_name varchar(255) NOT NULL,
  building_no int(11) NOT NULL,
  PRIMARY KEY (room_no),
  KEY building_no (building_no),
CONSTRAINT rooms_ibfk_1 
  FOREIGN KEY (building_no) 
  REFERENCES buildings (building_no) 
  ON DELETE CASCADE
) ENGINE=InnoDB;

我想查询模式中具有外键约束的每个表并了解其他选项。 我尝试过以下查询:

select * from INFORMATION_SCHEMA.KEY_COLUMN_USAGE;

select *
from INFORMATION_SCHEMA.TABLE_CONSTRAINTS
where CONSTRAINT_TYPE = 'FOREIGN KEY';

不幸的是，他们没有给我删除或更新操作。

Answer 1

如果您的表是 INNODB(我假设它们已被赋予外键)，请查看 INFORMATION_SCHEMA.SYS_FOREIGN 。从文档中，type 字段为您提供 ON DELETE/ON UPDATE 操作:

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

您可以通过FOR_NAME或REF_NAME进行查询。