【Mysql】外健常用

关联外健，当删除aaaa表中的数据会同时删除xxxx中的数据

ALTER TABLE 表名
ADD CONSTRAINT 表名_1
FOREIGN KEY (关联字段)
REFERENCES 关联表名(关联字段) 这里是关联触发删除的表
ON DELETE CASCADE;

示范：
ALTER TABLE xxxx
ADD CONSTRAINT xxxx_1
FOREIGN KEY (id)
REFERENCES aaaa(id) 
ON DELETE CASCADE;

查询外健

SELECT
    CONSTRAINT_NAME,
    COLUMN_NAME,
    REFERENCED_TABLE_NAME,
    REFERENCED_COLUMN_NAME
FROM information_schema.KEY_COLUMN_USAGE
WHERE TABLE_SCHEMA = '表名'

删除外健

ALTER TABLE aaaa DROP FOREIGN KEY aaaa_1;