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假设学生表叫student,课程表叫class,选课表叫choose
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1.三层嵌套的问题
select student.name from student where student.id IN
(select choose.sid from choose where choose.cid NOT IN
(select class.id from class where class.teacher='李明'))
2.一个内连接，一个嵌套
select student.name,avg(choose.score) from
student inner join choose on student.id=choose.sid
where student.id IN
(select choose.sid from choose
where choose.score'60'
group by choose.sid
having count(choose.sid)=2)
gruop by student.id
3.一个联合查询，一个嵌套查询
select student.name from student
where student.id IN
(select c1.sid from choose c1 where choose.cid='1'
union
select c2.sid from choose c2 where choose.cid='2'
on c1.sid=c2.sid
)
4.其实就是自连接查询和行列交换的问题：
select student.id,
(case choose.id when '1' then choose.score end) as 1号课成绩,
(case choose.id when '2' then choose.score end) as 2号课成绩,
from student inner join choose on student.id=choose.sid sc1,
student inner join choose on student.id=choose.sid sc2
where sc1.id='1'
and sc2.id='2'
and sc1.scoresc2.score
sqlserver的查询语句和插入更新语句怎么用
1、说明：复制表(只复制结构,源表名：a 新表名：b)
select * into b from a where 11（仅用于SQlServer）
2、说明：拷贝表(拷贝数据,源表名：a 目标表名：b)
insert into b(a, b, c) select d,e,f from a
将两条查询语句作为子查询的一部分连表.
select t1.count1+t2.count2 as 'countSum',t1.branch
(select count as count1, branch from table1 group by branch)t1
(select count as count2, branch from table2 group by branch)t2 on t1.branch =t2.branch
这种写法有一个潜在的限制,t1中的branch 必须包含t2,所以你的需求一般这么写:
select sum(counts)counts,branch
from(select * from(select count as counts, branch from table1 group by branch)t1
union
select * from(select count as counts, branch from table2 group by branch )t1)t
group by branch