经典的三表练习 sql
create table s --学生表(
sid int,
sname varchar(20) null,
)
create table c --课程表
(
cid int,
cname varchar(20) null
)
create table sc --学生选课表
(
tempid int,
sid int,
cid int ,
grade int null --成绩
)
insert into s values('1','sky')
insert into s values('2','music')
insert into s values('3','jacky')
insert into s values('4','mabel')
insert into c values('1','English')
insert into c values('2','Math')
insert into c values('3','Language')
insert into c values('4','Politic')
insert into sc values('1','1','1','99')
insert into sc values('2','1','2','100')
insert into sc values('3','2','1','50')
insert into sc values('4','2','2','60')
select * from s,c,sc where s.sid=sc.sid and c.cid=sc.cid --查出所有选了课的人
select * from s inner join sc on s.sid=sc.sid order by grade desc
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