SQL server 外键

给数据库的表添加一列：
alter table 表名 add 列名 类型 null
例子：
alter table UserInfo add [Address] nvarchar(32) null

代码的方式：给列添加默认值约束：
alter table 表名 add constraint 约束的名字 default(0) for DelFlag

例子：
alter table UserInfo add constraint DF_UserInfo_DelFlag default(0) for DelFlag

数据库的表删除一个约束和列
alter table UserInfo drop constraint DF_UserInfo_DelFlag
go
alter table UserInfo drop column DelFlag
go

修改一个列
alter table UserInfo drop column [address]
nvarchar(64) null

要求产品数量限制在 0~100：
alter table Product add constraint CK_Product_CountNumber Check(CountNumber>0 and CountNumber<100)

添加一个外键关系
alter table Product add constraint EK_Product_Category foreign key (CategoryId) references Category(CatId)

posted @ 2020-01-07 15:09  Attractor  阅读(217)  评论(0)  编辑  收藏  举报 
                                                                                                                                                                                                        
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