这篇文章主要介绍了50条sql查询技巧、查询语句示例,本文以学生表、课程表、成绩表、教师表为例,讲解不同需求下的sql语句写法,需要的朋友可以参考下
student(s#,sname,sage,ssex) 学生表
course(c#,cname,t#) 课程表
sc(s#,c#,score) 成绩表
teacher(t#,tname) 教师表
问题：
1、查询“001”课程比“002”课程成绩高的所有学生的学号；
select a.s# from (select s#,score from sc where c#='001') a,(select s#,score
from sc where c#='002') b
where a.score>b.score and a.s#=b.s#;
2、查询平均成绩大于60分的同学的学号和平均成绩；
select s#,avg(score)
from sc
group by s# having avg(score) >60;
3、查询所有同学的学号、姓名、选课数、总成绩；
select student.s#,student.sname,count(sc.c#),sum(score)
from student left outer join sc on student.s#=sc.s#
group by student.s#,sname
4、查询姓“李”的老师的个数；
select count(distinct(tname))
from teacher
where tname like '李%';
5、查询没学过“叶平”老师课的同学的学号、姓名；
select student.s#,student.sname
from student
where s# not in (select distinct( sc.s#) from sc,course,teacher where sc.c#=course.c# and teacher.t#=course.t# and teacher.tname='叶平');
6、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
select student.s#,student.sname from student,sc where student.s#=sc.s# and sc.c#='001'and exists( select * from sc as sc_2 where sc_2.s#=sc.s# and sc_2.c#='002');
7、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
select s#,sname
from student
where s# in (select s# from sc ,course ,teacher where sc.c#=course.c# and teacher.t#=course.t# and teacher.tname='叶平' group by s# having count(sc.c#)=(select count(c#) from course,teacher where teacher.t#=course.t# and tname='叶平'));
8、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；
select s#,sname from (select student.s#,student.sname,score ,(select score from sc sc_2 where sc_2.s#=student.s# and sc_2.c#='002') score2
from student,sc where student.s#=sc.s# and c#='001') s_2 where score2 <score;
9、查询所有课程成绩小于60分的同学的学号、姓名；
select s#,sname
from student
where s# not in (select student.s# from student,sc where s.s#=sc.s# and score>60);
10、查询没有学全所有课的同学的学号、姓名；
select student.s#,student.sname
from student,sc
where student.s#=sc.s# group by student.s#,student.sname having count(c#) <(select count(c#) from course);
11、查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名；
select s#,sname from student,sc where student.s#=sc.s# and c# in select c# from sc where s#='1001';
12、查询至少学过学号为“001”同学所有一门课的其他同学学号和姓名；
select distinct sc.s#,sname
from student,sc
where student.s#=sc.s# and c# in (select c# from sc where s#='001');
13、把“sc”表中“叶平”老师教的课的成绩都更改为此课程的平均成绩；
update sc set score=(select avg(sc_2.score)
from sc sc_2
where sc_2.c#=sc.c# ) from course,teacher where course.c#=sc.c# and course.t#=teacher.t# and teacher.tname='叶平');
14、查询和“1002”号的同学学习的课程完全相同的其他同学学号和姓名；
select s# from sc where c# in (select c# from sc where s#='1002')
group by s# having count(*)=(select count(*) from sc where s#='1002');
15、删除学习“叶平”老师课的sc表记录；
delect sc
from course ,teacher
where course.c#=sc.c# and course.t#= teacher.t# and tname='叶平';
16、向sc表中插入一些记录，这些记录要求符合以下条件：没有上过编号“003”课程的同学学号、2、
号课的平均成绩；
insert sc select s#,'002',(select avg(score)
from sc where c#='002') from student where s# not in (select s# from sc where c#='002');
17、按平均成绩从高到低显示所有学生的“数据库”、“企业管理”、“英语”三门的课程成绩，按如下形式显示： 学生id,,数据库,企业管理,英语,有效课程数,有效平均分
select s# as 学生id
,(select score from sc where sc.s#=t.s# and c#='004') as 数据库
,(select score from sc where sc.s#=t.s# and c#='001') as 企业管理
,(select score from sc where sc.s#=t.s# and c#='006') as 英语
,count(*) as 有效课程数, avg(t.score) as 平均成绩
from sc as t
group by s#
order by avg(t.score)
18、查询各科成绩最高和最低的分：以如下形式显示：课程id，最高分，最低分
select l.c# as 课程id,l.score as 最高分,r.score as 最低分
from sc l ,sc as r
where l.c# = r.c# and
l.score = (select max(il.score)
from sc as il,student as im
where l.c# = il.c# and im.s#=il.s#
group by il.c#)
and
r.score = (select min(ir.score)
from sc as ir
where r.c# = ir.c#
group by ir.c#
);
19、按各科平均成绩从低到高和及格率的百分数从高到低顺序
select t.c# as 课程号,max(course.cname)as 课程名,isnull(avg(score),0) as 平均成绩
,100 * sum(case when isnull(score,0)>=60 then 1 else 0 end)/count(*) as 及格百分数
from sc t,course
where t.c#=course.c#
group by t.c#
order by 100 * sum(case when isnull(score,0)>=60 then 1 else 0 end)/count(*) desc
20、查询如下课程平均成绩和及格率的百分数(用1行显示): 企业管理（001），马克思（002），oo¨ （003），数据库（004）
select sum(case when c# ='001' then score else 0 end)/sum(case c# when '001' then 1 else 0 end) as 企业管理平均分
,100 * sum(case when c# = '001' and score >= 60 then 1 else 0 end)/sum(case when c# = '001' then 1 else 0 end) as 企业管理及格百分数
,sum(case when c# = '002' then score else 0 end)/sum(case c# when '002' then 1 else 0 end) as 马克思平均分
,100 * sum(case when c# = '002' and score >= 60 then 1 else 0 end)/sum(case when c# = '002' then 1 else 0 end) as 马克思及格百分数
,sum(case when c# = '003' then score else 0 end)/sum(case c# when '003' then 1 else 0 end) as uml平均分
,100 * sum(case when c# = '003' and score >= 60 then 1 else 0 end)/sum(case when c# = '003' then 1 else 0 end) as uml及格百分数
,sum(case when c# = '004' then score else 0 end)/sum(case c# when '004' then 1 else 0 end) as 数据库平均分
,100 * sum(case when c# = '004' and score >= 60 then 1 else 0 end)/sum(case when c# = '004' then 1 else 0 end) as 数据库及格百分数
from sc
21、查询不同老师所教不同课程平均分从高到低显示
select max(z.t#) as 教师id,max(z.tname) as 教师姓名,c.c# as 课程ｉｄ,max(c.cname) as 课程名称,avg(score) as 平均成绩
from sc as t,course as c ,teacher as z
where t.c#=c.c# and c.t#=z.t#
group by c.c#
order by avg(score) desc
22、查询如下课程成绩第 3 名到第 6 名的学生成绩单：企业管理（001），马克思（002），uml （003），数据库（004）
[学生id],[学生姓名],企业管理,马克思,uml,数据库,平均成绩
select distinct top 3
sc.s# as 学生学号,
student.sname as 学生姓名 ,
t1.score as 企业管理,
t2.score as 马克思,
t3.score as uml,
t4.score as 数据库,
isnull(t1.score,0) + isnull(t2.score,0) + isnull(t3.score,0) + isnull(t4.score,0) as 总分
from student,sc left join sc as t1
on sc.s# = t1.s# and t1.c# = '001'
left join sc as t2
on sc.s# = t2.s# and t2.c# = '002'
left join sc as t3
on sc.s# = t3.s# and t3.c# = '003'
left join sc as t4
on sc.s# = t4.s# and t4.c# = '004'
where student.s#=sc.s# and
isnull(t1.score,0) + isnull(t2.score,0) + isnull(t3.score,0) + isnull(t4.score,0)
not in
(select
distinct
top 15 with ties
isnull(t1.score,0) + isnull(t2.score,0) + isnull(t3.score,0) + isnull(t4.score,0)
from sc
left join sc as t1
on sc.s# = t1.s# and t1.c# = 'k1'
left join sc as t2
on sc.s# = t2.s# and t2.c# = 'k2'
left join sc as t3
on sc.s# = t3.s# and t3.c# = 'k3'
left join sc as t4
on sc.s# = t4.s# and t4.c# = 'k4'
order by isnull(t1.score,0) + isnull(t2.score,0) + isnull(t3.score,0) + isnull(t4.score,0) desc);
23、统计列印各科成绩,各分数段人数:课程id,课程名称,[100-85],[85-70],[70-60],[ <60]
select sc.c# as 课程id, cname as 课程名称
,sum(case when score between 85 and 100 then 1 else 0 end) as [100 - 85]
,sum(case when score between 70 and 85 then 1 else 0 end) as [85 - 70]
,sum(case when score between 60 and 70 then 1 else 0 end) as [70 - 60]
,sum(case when score < 60 then 1 else 0 end) as [60 -]
from sc,course
where sc.c#=course.c#
group by sc.c#,cname;
24、查询学生平均成绩及其名次
select 1+(select count( distinct 平均成绩)
from (select s#,avg(score) as 平均成绩
from sc
group by s#
) as t1
where 平均成绩 > t2.平均成绩) as 名次,
s# as 学生学号,平均成绩
from (select s#,avg(score) 平均成绩
from sc
group by s#
) as t2
order by 平均成绩 desc;
25、查询各科成绩前三名的记录:(不考虑成绩并列情况)
select t1.s# as 学生id,t1.c# as 课程id,score as 分数
from sc t1
where score in (select top 3 score
from sc
where t1.c#= c#
order by score desc
)
order by t1.c#;
26、查询每门课程被选修的学生数
select c#,count(s#) from sc group by c#;
27、查询出只选修了一门课程的全部学生的学号和姓名
select sc.s#,student.sname,count(c#) as 选课数
from sc ,student
where sc.s#=student.s# group by sc.s# ,student.sname having count(c#)=1;
28、查询男生、女生人数
select count(ssex) as 男生人数 from student group by ssex having ssex='男';
select count(ssex) as 女生人数 from student group by ssex having ssex='女'；
29、查询姓“张”的学生名单
select sname from student where sname like '张%';
30、查询同名同性学生名单，并统计同名人数
select sname,count(*) from student group by sname having count(*)>1;
31、1981年出生的学生名单(注：student表中sage列的类型是datetime)
select sname, convert(char (11),datepart(year,sage)) as age
from student
where convert(char(11),datepart(year,sage))='1981';
32、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列
select c#,avg(score) from sc group by c# order by avg(score),c# desc ;
33、查询平均成绩大于85的所有学生的学号、姓名和平均成绩
select sname,sc.s# ,avg(score)
from student,sc
where student.s#=sc.s# group by sc.s#,sname having avg(score)>85;
34、查询课程名称为“数据库”，且分数低于60的学生姓名和分数
select sname,isnull(score,0)
from student,sc,course
where sc.s#=student.s# and sc.c#=course.c# and course.cname='数据库'and score <60;
35、查询所有学生的选课情况；
select sc.s#,sc.c#,sname,cname
from sc,student,course
where sc.s#=student.s# and sc.c#=course.c# ;
36、查询任何一门课程成绩在70分以上的姓名、课程名称和分数；
select distinct student.s#,student.sname,sc.c#,sc.score
from student,sc
where sc.score>=70 and sc.s#=student.s#;
37、查询不及格的课程，并按课程号从大到小排列
select c# from sc where scor e <60 order by c# ;
38、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；
select sc.s#,student.sname from sc,student where sc.s#=student.s# and score>80 and c#='003';
39、求选了课程的学生人数
select count(*) from sc;
40、查询选修“叶平”老师所授课程的学生中，成绩最高的学生姓名及其成绩
select student.sname,score
from student,sc,course c,teacher
where student.s#=sc.s# and sc.c#=c.c# and c.t#=teacher.t# and teacher.tname='叶平' and sc.score=(select max(score)from sc where c#=c.c# );
41、查询各个课程及相应的选修人数
select count(*) from sc group by c#;
42、查询不同课程成绩相同的学生的学号、课程号、学生成绩
select distinct a.s#,b.score from sc a ,sc b where a.score=b.score and a.c# <>b.c# ;
43、查询每门功成绩最好的前两名
select t1.s# as 学生id,t1.c# as 课程id,score as 分数
from sc t1
where score in (select top 2 score
from sc
where t1.c#= c#
order by score desc
)
order by t1.c#;
44、统计每门课程的学生选修人数（超过10人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，查询结果按人数降序排列，若人数相同，按课程号升序排列
select c# as 课程号,count(*) as 人数
from sc
group by c#
order by count(*) desc,c#
45、检索至少选修两门课程的学生学号
select s#
from sc
group by s#
having count(*) > = 2
46、查询全部学生都选修的课程的课程号和课程名
select c#,cname
from course
where c# in (select c# from sc group by c#)
47、查询没学过“叶平”老师讲授的任一门课程的学生姓名
select sname from student where s# not in (select s# from course,teacher,sc where course.t#=teacher.t# and sc.c#=course.c# and tname='叶平');
48、查询两门以上不及格课程的同学的学号及其平均成绩
select s#,avg(isnull(score,0)) from sc where s# in (select s# from sc where score <60 group by s# having count(*)>2)group by s#;
49、检索“004”课程分数小于60，按分数降序排列的同学学号
select s# from sc where c#='004'and score <60 order by score desc;
50、删除“002”同学的“001”课程的成绩
delete from sc where s#='001'and c#='001';
