think in java interview-高级开发人员面试宝典(六)

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';