原文地址：sql语句多表查询(学生表/课程表/教师表/成绩表 )作者：海豚湾孬蛋
问题及描述： --1.学生表
Student(S#,Sname,Sage,Ssex) --S# 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别 --2.课程表
Course(C#,Cname,T#) --C# --课程编号,Cname 课程名称,T# 教师编号 --3.教师表
Teacher(T#,Tname) --T# 教师编号,Tname 教师姓名 --4.成绩表
SC(S#,C#,score) --S# 学生编号,C# 课程编号,score 分数 */
--创建测试数据
create table Student(S# varchar(10),Sname nvarchar(10),Sage datetime,Ssex nvarchar(10)) insert into Student values('01' , N'赵雷' , '1990-01-01' , N'男') insert into Student values('02' , N'钱电' , '1990-12-21' , N'男') insert into Student values('03' , N'孙风' , '1990-05-20' , N'男') insert into Student values('04' , N'李云' , '1990-08-06' , N'男') insert into Student values('05' , N'周梅' , '1991-12-01' , N'女') insert into Student values('06' , N'吴兰' , '1992-03-01' , N'女') insert into Student values('07' , N'郑竹' , '1989-07-01' , N'女') insert into Student values('08' , N'王菊' , '1990-01-20' , N'女')
create table Course(C# varchar(10),Cname nvarchar(10),T# varchar(10)) insert into Course values('01' , N'语文' , '02') insert into Course values('02' , N'数学' , '01') insert into Course values('03' , N'英语' , '03')
create table Teacher(T# varchar(10),Tname nvarchar(10)) insert into Teacher values('01' , N'张三') insert into Teacher values('02' , N'李四') insert into Teacher values('03' , N'王五')
create table SC(S# varchar(10),C# varchar(10),score decimal(18,1)) insert into SC values('01' , '01' , 80) insert into SC values('01' , '02' , 90) insert into SC values('01' , '03' , 99) insert into SC values('02' , '01' , 70) insert into SC values('02' , '02' , 60) insert into SC values('02' , '03' , 80) insert into SC values('03' , '01' , 80) insert into SC values('03' , '02' , 80) insert into SC values('03' , '03' , 80) insert into SC values('04' , '01' , 50) insert into SC values('04' , '02' , 30) insert into SC values('04' , '03' , 20) insert into SC values('05' , '01' , 76) insert into SC values('05' , '02' , 87) insert into SC values('06' , '01' , 31) insert into SC values('06' , '03' , 34) insert into SC values('07' , '02' , 89) insert into SC values('07' , '03' , 98) go
--1、查询\课程比\课程成绩高的学生的信息及课程分数 --1.1、查询同时存在\课程和\课程的情况
select a.* , b.score [课程'01'的分数],c.score [课程'02'的分数] from Student a , SC b , SC c where a.S# = b.S# and a.S# = c.S# and b.C# = '01' and c.C# = '02' and b.score > c.score --1.2、查询同时存在\课程和\课程的情况和存在\课程但可能不存在\课程的情况(不存在时显示为null)(以下存在相同内容时不再解释)
select a.* , b.score [课程\的分数],c.score [课程\的分数] from Student a left join SC b on a.S# = b.S# and b.C# = '01'
left join SC c on a.S# = c.S# and c.C# = '02' where b.score > isnull(c.score,0)
--2、查询\课程比\课程成绩低的学生的信息及课程分数 --2.1、查询同时存在\课程和\课程的情况
select a.* , b.score [课程'01'的分数],c.score [课程'02'的分数] from Student a , SC b , SC c where a.S# = b.S# and a.S# = c.S# and b.C# = '01' and c.C# = '02' and b.score < c.score --2.2、查询同时存在\课程和\课程的情况和不存在\课程但存在\课程的情况 select a.* , b.score [课程\的分数],c.score [课程\的分数] from Student a left join SC b on a.S# = b.S# and b.C# = '01' left join SC c on a.S# = c.S# and c.C# = '02' where isnull(b.score,0) < c.score
--3、查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩 select a.S# , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score from Student a , sc b where a.S# = b.S# group by a.S# , a.Sname
having cast(avg(b.score) as decimal(18,2)) >= 60 order by a.S#
--4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩 --4.1、查询在sc表存在成绩的学生信息的SQL语句。
select a.S# , a.Sname , cast(avg(b.score) as decimal(18,2)) avg_score from Student a , sc b where a.S# = b.S# group by a.S# , a.Sname
having cast(avg(b.score) as decimal(18,2)) < 60 order by a.S#
--4.2、查询在sc表中不存在成绩的学生信息的SQL语句。
select a.S# , a.Sname , isnull(cast(avg(b.score) as decimal(18,2)),0) avg_score
from Student a left join sc b on a.S# = b.S# group by a.S# , a.Sname
having isnull(cast(avg(b.score) as decimal(18,2)),0) < 60 order by a.S#
--5、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩 --5.1、查询所有有成绩的SQL。
select a.S# [学生编号], a.Sname [学生姓名], count(b.C#) 选课总数, sum(score) [所有课程的总成绩]
from Student a , SC b where a.S# = b.S# group by a.S#,a.Sname order by a.S#
--5.2、查询所有(包括有成绩和无成绩)的SQL。
select a.S# [学生编号], a.Sname [学生姓名], count(b.C#) 选课总数, sum(score) [所有课程的总成绩]
from Student a left join SC b on a.S# = b.S# group by a.S#,a.Sname order by a.S#
--6、查询\李\姓老师的数量 --方法1
select count(Tname) [\李\姓老师的数量] from Teacher where Tname like N'李%' --方法2
select count(Tname) [\李\姓老师的数量] from Teacher where left(Tname,1) = N'李'
--7、查询学过\张三\老师授课的同学的信息 select distinct Student.* from Student , SC , Course , Teacher
where Student.S# = SC.S# and SC.C# = Course.C# and Course.T# = Teacher.T# and
Teacher.Tname = N'张三' order by Student.S#
--8、查询没学过\张三\老师授课的同学的信息
select m.* from Student m where S# not in (select distinct SC.S# from SC , Course , Teacher where SC.C# = Course.C# and Course.T# = Teacher.T# and Teacher.Tname = N'张三') order by m.S#
--9、查询学过编号为\并且也学过编号为\的课程的同学的信息 --方法1
select Student.* from Student , SC where Student.S# = SC.S# and SC.C# = '01' and exists (Select 1 from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# = '02') order by Student.S# --方法2
select Student.* from Student , SC where Student.S# = SC.S# and SC.C# = '02' and exists (Select 1 from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# = '01') order by Student.S# --方法3
select m.* from Student m where S# in (
select S# from (
select distinct S# from SC where C# = '01' union all
select distinct S# from SC where C# = '02' ) t group by S# having count(1) = 2 )
order by m.S#
--10、查询学过编号为\但是没有学过编号为\的课程的同学的信息 --方法1
select Student.* from Student , SC where Student.S# = SC.S# and SC.C# = '01' and not exists (Select 1 from SC SC_2 where SC_2.S# = SC.S# and SC_2.C# = '02') order by Student.S#