经典50道 sql面试及答案
SQL数据库面试题以及答案（50例题）原文：https://blog.csdn.net/qq_30184931/article/details/79200526
Student(S#,Sname,Sage,Ssex)学生表
S#：学号
Sname：学生姓名
Sage：学生年龄
Ssex：学生性别
Course(C#,Cname,T#)课程表
C#：课程编号
Cname：课程名称
T#：教师编号
SC(S#,C#,score)成绩表
S#：学号
C#：课程编号
score：成绩
Teacher(T#,Tname)教师表
T#：教师编号：
Tname：教师名字
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、查询没有学过“叶平”老师可的同学的学号、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 Teahcer.Tname =‘叶平’);
6、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’));
7、查询学过“011”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’);
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”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(s2_Score) From sc s2 Where s2.c#=sc.c#)
Where c# IN
(Select c# From sc cs INNER JOIN Teacher tc ON cs.t#=tc.t# WHERE 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、002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#=‘003’);
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 平局成绩
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：以如下的形式显示：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 R
where L.c# = R.c#
and L.score = (select max(IL.score)
from sc 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&UML （003），数据库（004）：
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,
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)：
23、统计下列各科成绩，各分数段人数：课程ID，课程名称，[100-85],[85-70],[70-60],[ 小于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)
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、查询同名同姓的学生名单，并统计同名人数：
select sanme,count()
from student
group by sname
havang 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;
33、查询每门课程的平均成绩，结果按平均成绩升序排序，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;
34、查询课程名称为“数据库”，且分数低于60的学生名字和分数：
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的排列：
select c#
from sc
where score<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和学号、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、查询每门课程成绩最好的前两名：
select t1.s# as 学生ID,t1.c# 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序，若人数相同，按课程号升序排序：
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、查询全部学生选修的课程和课程号和课程名：
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以及其平均成绩：
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
