SQL 级联删除与级联更新的方法

231 阅读 0 评论 153 点赞

我是靠谱客的博主孝顺火车，最近开发中收集的这篇文章主要介绍SQL 级联删除与级联更新的方法，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

复制代码代码如下:

on delete cascade

当你更新或删除主键表时，那么外键表也会跟随一起更新或删除,需要在建表时设置级联属性

CREATE TABLE Countries(CountryId INT PRIMARY KEY)
INSERT INTO Countries (CountryId) VALUES (1)
INSERT INTO Countries (CountryId) VALUES (2)
INSERT INTO Countries (CountryId) VALUES (3)

CREATE TABLE Cities( CityId INT PRIMARY KEY ,CountryId INT REFERENCES Countries ON DELETE CASCADE);
INSERT INTO Cities VALUES(1,1)
INSERT INTO Cities VALUES(2,1)
INSERT INTO Cities VALUES(3,2)

CREATE TABLE Buyers(CustomerId INT PRIMARY KEY ,CityId INT REFERENCES Cities ON DELETE CASCADE);
INSERT INTO Buyers VALUES(1,1),
INSERT INTO Buyers VALUES(2,1)
INSERT INTO Buyers VALUES(3,2)

此外还有级联更新
on update cascade