CREATE TABLE s(s# int not null primary key,s_name varchar(8) not null);
CREATE TABLE c (c# int not null primary key,c_name varchar(8) not null);
CREATE TABLE cs(c# int not null,s# int not null,cj tinyint not null,
primary key (c#,s#),foreign key(s#) references s(s#),foreign key(c#) references c(c#))
insert into s values(1,'saa');
insert into c values(1,'caa');
--这句是对的
insert into cs values(1,1,86);
--这句是错的,sql会报错,应为s表的s#列里没有2
insert into cs values(2,1,45);