CHECK约束
create table student( Sno int not null primary key, age int check(age between 1 and 100) sex char(2) check(sex in('男bai','女du') DempNo int)
修改取值范围:https://blog.csdn.net/qq_27494201/article/details/102507259
撤销 CHECK 约束
https://zhidao.baidu.com/question/2052026833620410067.html
添加CHECK约束:https://blog.csdn.net/qq_43551373/article/details/87865739
SQL Server中的约束(六种约束):https://www.cnblogs.com/xiaolinshushu/p/3256110.html