写了这么多JAVA基础，来点SQL吧！
一般面试时考SQL，主要就是考你“统计分析”这一块，下面我们来看面试官经常采用的手段。
由4张简单的不能再简单的表，演变出50道SQL
哈哈哈哈，够这个面试官面个15，20个人，不带重复的了，而且每个SQL你真的不动动脑子还写不出呢，你别不服气，下面开始。
表结构：
表Student
(S#,Sname,Sage,Ssex) 学生表
S#
|
student_no |
Sage
|
student_age
|
Ssex
|
student_sex |
表Course
(C#,Cname,T#) 课程表
C#
|
course_no |
| Cname |
course_name |
| T# |
teacher_no |
表SC（学生与课程的分数mapping 表）
(S#,C#,score) 成绩表
| S# |
student_no |
| C# |
course_no |
| score |
分数啦 |
表Teacher
(T#,Tname) 教师表
| T# |
teacher_no |
| Tname |
teacher_name |
50道问题开始
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')
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#) fromSC,Course,Teacher
where SC.C#=Course.C#and Teacher.T#=Course.T#
andTeacher.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
fromStudent,SC where Student.S#=SC.S#
andSC.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#
andTeacher.T#=Course.T#
and Teacher.Tname='叶平'group
by S# having
count(SC.C#)=(select
count(C#) fromCourse,Teacher
whereTeacher.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#
andC#='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#
fromStudent,SC where S.S#=SC.S#
andscore>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
whereStudent.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
whereStudent.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# )
fromCourse,Teacher where Course.C#=SC.C#
andCourse.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；
DelectSC
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#
notin (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
ASIL,Student AS IM
WHERE L.C#
=IL.C# and IM.S#=IL.S#
GROUP
BYIL.C#)
AND
R.Score= (SELECT
MIN(IR.score)
FROM SC
ASIR
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），（002），OO&UML （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 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 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），（002），UML （003），数据库（004）
[学生ID],[学生姓名],企业管理,,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 ,
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';
转载地址：http://blog.csdn.net/lifetragedy/article/details/9935699
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