SQL数据库面试题以及答案（50例题）

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Student(Sid,Sname,Sage,Ssex)学生表

Sid：学号

Sname：学生姓名

Sage：学生年龄

Ssex：学生性别

Course(Cid,Cname,T#)课程表

Cid：课程编号

Cname：课程名称

Tid：教师编号

SC(Sid,Cid,score)成绩表

Sid：学号

Cid：课程编号

score：成绩

Teacher(Tid,Tname)教师表

Tid：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.sid from 
(select sid,score from sc where cid='001')a,
(select sid,score from sc where cid='002')b 
where a.sid = b.sid and a.scoreb.score;

2、查询平均成绩大于60分的同学的学号和平均成绩

select sid,avg(score) from sc
group by sid 
having avg(score)60;

3、查询所有同学的学号、姓名、选课数、总成绩

select s.sid,s.sname,count_cid as 选课数, 
sum_score  as 总成绩
from student s
left join 
(select sid,count(cid) as count_cid,sum(score) as sum_score 
from sc group by sid )sc
on s.sid = sc.sid;

4、查询姓‘李’的老师的个数：

select count(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 s.sid,s.sname 
from student as s 
where s.sid not in (
    select DISTINCT sid 
    from sc as sc 
    where sc.cid in (
        select cid 
        from course as c 
        left join teacher as t on c.tid = t.tid 
        where t.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.sid,s.sname 
from student as s 
where s.sid in (
    select distinct sc.sid 
  from sc as sc 
  where sc.cid in (
    select cid 
    from course as c 
    left join teacher as t on c.tid = t.tid 
    where t.tname = '叶平')
        group by sc.sid 
    HAVING count(cid)=
    (select count(cid) 
     from course as c left join teacher as t on c.tid = t.tid 
     where t.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 s.sid,s.sname 
from student as s 
left join sc as sc on s.sid = sc.sid
where sc.cid = '001'
and EXISTS(
  select * from sc as sc_2 
  where sc.sid = sc_2.sid 
  and sc_2.cid='002');

select s.sid,s.sname
from student as s 
left join sc as sc 
on sc.sid = s.sid
where sc.cid = '001'
and s.sid in (
  select sid from sc as sc_2 
  where sc_2.cid='002' 
  and sc_2.sid = sc.sid);

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 sid,sname
from (select student.sid,student.sname,score,
     (select score from sc as sc_2 
      where sc_2.sid = student.sid 
      and sc_2.cid = '002') as score2 
      from student,sc 
      where student.sid=sc.sid and cid = '001') s_2
where score2score;

9、查询所有课程成绩小于60的同学的学号、姓名：

select sid,sname
from student
where sid not in 
(select s.sid 
from student s,sc 
where s.sid=sc.sid and score60 );

select sid,sname
from student s
where not EXISTS (
select s.sid from sc 
where sc.sid = s.sid and sc.score60);

10、查询没有学全所有课的同学的学号、姓名：

select s.sid,s.sname
from student s ,sc sc 
where s.sid = sc.sid
group by s.sid,s.sname
having count(sc.cid)(
select count(cid) 
from course);

select s.sid,s.sname
from student s 
right join sc sc on s.sid = sc.sid
group by s.sid,s.sname
having count(sc.cid)
(select count(cid) 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 student.sid,sname
from student,sc 
where student.sid = sc.sid
and cid in 
(select cid from sc where sid='1001');

select s.sid,s.sname
from sc sc left join student as s
on sc.sid = s.sid
where sc.cid in (select cid from sc where sid='1001');

select sc_1.sid,s.sname
from sc sc_1 left join student as s
on sc_1.sid = s.sid
where 
exists (select sc_2.cid from sc as sc_2 
where sc_1.cid = sc_2.cid 
and sc_2.sid = '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；

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.cid = sc.cid)
where cid in 
(select c.cid from course c 
left join teacher t on t.tid = c.tid 
where t.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 sc_1.sid 
from (select cid from sc where sid='1002')a
left join sc sc_1 on a.cid = sc_1.cid
where sc_1.sid'1002' 
group by sc_1.sid 
having count(sc_1.cid) = 
(select count(cid) from sc where sid='1002');

select a.sid,s.sname from 
(select sid,GROUP_CONCAT(cid order by cid separator ',') as cid_str 
from sc where sid='1002')b,
(select sid,GROUP_CONCAT(cid order by cid separator ',') as cid_str 
from sc group by sid)a
left join student s 
on a.sid = s.sid
where a.cid_str = b.cid_str and a.sid'1002';

15、删除学习“叶平”老师课的SC表记录：

delete from sc WHERE
cid in (
select c.cid from course c 
LEFT JOIN teacher t on c.tid=t.tid 
where t.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 into sc select sid,'002',
(select avg(score) from sc where cid='0022')
from student 
where sid not in (select sid from sc where cid='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 sid as 学生id,
(SELECT score from sc 
where sc.sid = t.sid and cid='004') as 数据库,
(select score from sc 
where sc.sid = t.sid and cid='001') as 企业管理,
(select score from sc 
where sc.sid = t.sid and cid='015') as 英语,
count(cid) as 有效课程数, avg(t.score) as 平均成绩
from sc as t 
group by sid
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.cid as 课程id,l.score as 最高分,
r.score as 最低分
from sc l,sc r
where l.cid = r.cid
and l.score = 
(select max(t.score) from sc t 
where l.cid = t.cid group by t.cid)
and r.score = (select min(t.score) from sc t 
where r.cid = t.cid group by t.cid)
order by l.cid;

select cid as 课程id,max(score) as 最高分,
min(score) as 最低分
from sc 
group by cid;

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.cid as 课程号,
c.cname as 课程名,
COALESCE(avg(score),0) as 平均成绩,
100*sum(case 
when COALESCE(score,0)=60 
then 1 else 0 END)/count(*) as 及格百分数
from sc t
left join course c 
on t.cid = c.cid
group by t.cid
order by 100*sum(case 
when COALESCE(score,0)=60 
then 1 else 0 END)/count(*);

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 t.tid as 教师id,
t.tname as 教师姓名,
sc.cid as 课程id,
avg(score) as 平均成绩
from sc as sc
LEFT JOIN course c on sc.cid = c.cid
left join teacher t on c.tid = t.tid
group by sc.cid 
order by avg(sc.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.cid 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 score60 then 1 else 0 end) as '[60-0]'
from sc as sc 
left join course as c
on sc.cid = c.cid
group by sc.cid;

24、查询学生平均成绩及其名次：

select 1+(select count(distinct 平均成绩) 
from (select sid,avg(score) as 平均成绩 
from sc group by sid)t1 
where 平均成绩t2.平均成绩) as 名次,
sid as 学生学号,平均成绩 
from (select sid,avg(score) 平均成绩 from sc group by sid) 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 sid,cid,score
from sc sc_1
where (
select count(3) from sc sc_2 
where sc_1.cid = sc_2.cid 
and sc_2.score=sc_1.score)=2 
order by sc_1.cid
);

26、查询每门课程被选修的学生数：

select cid, count(sid)
from sc 
group by cid;

27、查询出只选修一门课程的全部学生的学号和姓名：

select sc.sid,s.sname,
count(sc.cid) as 课程数
from sc as sc
LEFT JOIN student as s
on sc.sid = s.sid
group by sc.sid
having count(sc.cid)=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(2) from student
where ssex = '女';

29、查询姓“张”的学生名单：

select sid,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 sname,count(8)
from student 
group by sname
having count(8)1;

31、1981年出生的学生名单（注：student表中sage列的类型是datetime）:

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 s.sname,sc.sid,avg(sc.score) as 平均成绩
from sc as sc
left join student as s 
on sc.sid = s.sid
group by sc.sid 
having avg(sc.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 cid,avg(score)
from sc 
group by cid
order by avg(score),cid 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 c.cname,s.sid,s.sname,sc.score
from course c
left join sc on sc.cid = c.cid
LEFT JOIN student s on s.sid = sc.sid
where c.cname = '数据库' and sc.score60;

35、查询所有学生的选课情况：

select sc.sid,sc.cid,s.sname,c.cname
from sc 
LEFT JOIN course c on sc.cid = c.cid
left join student s on sc.sid = s.sid;

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 s.sid,s.sname,sc.cid,sc.score
from sc 
left join student s on sc.sid = s.sid
left join course c on sc.cid = c.cid
where sc.score70;

37、查询不及格的课程，并按课程号从大到小的排列：

select cid
from sc 
where score60
ORDER BY cid;

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.sid,s.sname 
from sc 
left join student s on sc.sid = s.sid
where sc.cid = '003' and sc.score80;

39、求选了课程的学生人数：

select count(2) from 
(select distinct sid from sc)a;

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 s.sname,sc.score
from sc sc 
left join student s on sc.sid = s.sid
left join course c on sc.cid = c.cid
left join teacher t on c.tid = t.tid
where t.tname = '叶平'
and sc.score = (
select max(score) 
from sc sc_1 
where sc.cid = sc_1.cid);

41、查询各个课程及相应的选修人数：

select cid,count(*) from sc group by cid;

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.sid,a.cid,a.score
from sc as a ,sc as b 
where a.score = b.score
and a.cid  b.cid;

43、查询每门课程成绩最好的前两名：

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 cid as 课程号,count(8) as 选修人数
from sc
group by cid
HAVING count(sid)10
order by count(8) desc,cid;

45、检索至少选修两门课程的学生学号：

select sid
from sc
group by sid
having count(8)=2;

46、查询全部学生选修的课程和课程号和课程名：

select cid,cname
from course 
where cid in (select cid from sc group by cid);

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 sid not in (
    select sid 
    from sc,course,teacher 
    where course.tid = teacher.tid and sc.cid = course.cid 
    and teacher.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 sid,avg(COALESCE(score,0))
from sc
where sid in (
    select sid 
    from sc 
    where score60 
    group by sid 
    having count(8)2
)
group by sid;

49、检索“004”课程分数小于60，按分数降序排列的同学学号：

select sid,score
from sc
where cid='004'
and score60
order by score desc;

50、删除“002”同学的“001”课程的成绩：

delete from sc
where sid = '002'
and cid = '001';

来源：blog.csdn.net/hundan_520520/article/details/54881208

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