mysql怎么设置级联删除

这个在建表的时候就可以指定了

CREATE TABLE buildings (

building_no INT PRIMARY KEY AUTO_INCREMENT,

building_name VARCHAR(255) NOT NULL,

address VARCHAR(255) NOT NULL

)

CREATE TABLE rooms (

room_no INT PRIMARY KEY AUTO_INCREMENT,

room_name VARCHAR(255) NOT NULL,

building_no INT NOT NULL,

FOREIGN KEY (building_no)

REFERENCES buildings (building_no)

ON DELETE CASCADE

)

当执行

DELETE FROM buildings

WHERE

building_no = 2的时候，rooms表中的building_no =2的记录都会被删掉。

mysql:

1、先给B表添加主键列

alter table tableB add constraint b_PK primary key(date,channel)

2、将B表的组合主键关联到A表的外键组合键中

alter table tableB add constraint tableB_fk foreign key(date,channel) references tableA (date,channel) on DELETE CASCADE

3 delete from tableA where date =? and channel =? 就出发相关记录··~

create trigger update_id on a

for delete

as

Declare @qqlx_bid varchar(20)

Declare @qqlx_cid varchar(20)

--获得删除记录

select @qqlx_bid=bid,@qqlx_cid=cid from deleted

update b set bid=0 where bid=@qqlx_bid

update c set cid=0 where cid=@qqlx_cid

end

go

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