数据库约束（1）学习

use master;
go
if DB_ID('test') is not null
	drop database test;
go
    create database test;
go 
use test;
CREATE TABLE MovieExec (
    name		CHAR(30),
    address		VARCHAR(255),
    cert#		INT		PRIMARY KEY,--主键
    netWorth	INT
);

create table Studio(
	name char(30)  primary key ,
	address char(255),
	presC# int,
	foreign key(presC#) references MovieExec(cert#)
		ON delete set null   --删除时设置空
		on update cascade    --更新时置空
		--deferrble initially deferred 
);


CREATE TABLE MovieStar (
    name		CHAR(30),
	address		VARCHAR(255),
    gender		CHAR(1) constraint NoAndro check(gender in('F','M')),
    birthdate	CHAR(10),
    constraint NameIsKey PRIMARY KEY (name)    --constraint设置约束名
);

alter table MovieStar drop constraint NoAndro;  --删除约束
alter table MovieStar drop  constraint NameIsKey;   
alter table MovieStar add constraint NameIsKey primary Key(name);  --加入约束

exec sp_help 'MovieStar';  --查看表中的约束