参照完整性的实现策略 有三种策略:NO actioncascade还有就是设置为空值这个设置为空值怎么实现??举个列子 解决方案 » 免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货 create table Themes( ThemeID int primary key, ThemeName varchar(100),)create table Users( UserID int primary key, UserName varchar(100), ThemeID int constraint Users_ThemeID_FK references Themes(ThemeID) on delete set null --自己测试时改:on delete cascade --或者on delete no action)insert into Themes (ThemeID, ThemeName) values (1,'Default')insert into Themes (ThemeID, ThemeName) values (2,'Winter')insert into Users(UserID, UserName, ThemeID) values (1,'JSmith',null)insert into Users(UserID, UserName, ThemeID) values (2,'Ted',1)insert into Users(UserID, UserName, ThemeID) values (3,'Mary',2)--删除themes表themeid为1的记录DELETE themes WHERE themeid=1select * from usersgodrop table users,themes 不但可以设置为 null,还可以设置为默认值。 海量数据(TB级)sqlserver2008能够承受吗? 菜鸟:sql2000字段int添加空值后输出总显示0如何去掉? 一道sql查询问题,不知道怎么写查询语句,求教 为什么我的sqlserver里没有执行存储过程的选项? 我是新手,想请问一下闭包在数据库中的实际意义 问个弱弱的问题 为什么我的sql2005安装的时候出错 提示:共享内存提供程序: 超时错误 一个很常见,但很重要的问题 面试时候SQL查询优化问题,为此身价跌了不少 求一个简单三表联查 求助,oracle里面函数转换成SqlServer函数 求一带条件执行的触发器
(
ThemeID int primary key,
ThemeName varchar(100),
)create table Users
(
UserID int primary key,
UserName varchar(100),
ThemeID int constraint Users_ThemeID_FK references Themes(ThemeID)
on delete set null --自己测试时改:on delete cascade
--或者on delete no action
)insert into Themes (ThemeID, ThemeName) values (1,'Default')
insert into Themes (ThemeID, ThemeName) values (2,'Winter')insert into Users(UserID, UserName, ThemeID) values (1,'JSmith',null)
insert into Users(UserID, UserName, ThemeID) values (2,'Ted',1)
insert into Users(UserID, UserName, ThemeID) values (3,'Mary',2)--删除themes表themeid为1的记录
DELETE themes WHERE themeid=1select * from usersgo
drop table users,themes