Mysql 面试练手题

从网络收集的一些题，用来面试前练手，如有任何问题留言给我。侵删。

1.1查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数

select * from (select * from sc where cid = '01') a

inner join

(select *from sc where cid = '02') b on a.sid=b.sid;

1.2.查询存在" 01 "课程但可能不存在" 02 "课程的情况(不存在时显示为 null ) 

select * from (select *from sc where cid='01') a

    left join

      (select *from sc where cid ='02') b on a.sid = b.sid;

1.3.查询不存在"01 "课程但存在" 02 "课程的情况

select * from sc where sid =

(select sid from sc where sid not in(select sid from sc where cid = '01') and cid = '02');

2.查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩

Select a.sid, a.sname,b.avg_score from (select * from student) a inner join

(select sid, avg(score) as avg_score

from sc group by sid having avg(score) >= 60) b on a.sid = b.sid;

3.查询在 SC 表存在成绩的学生信息

select * from student where sid in (select sid from sc);

4. 查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )

select

a.sid,a.sname,count(b.cid),sum(b.score)

from student a left join sc b on a.sid = b.sid group by a.sid;

4.1 查有成绩的学生信息

Select *from student where sid in (select sid from sc);

Select a.sid,a.sname,count(b.cid),sum(b.score) from student a inner join sc b on a.sid = b.sid group by a.sid;

5.  查询「李」姓老师的数量

Select count(tid) count_sid from teacher where tname like”李%”;

6.  查询学过「张三」老师授课的同学的信息

Select * from student where sid in( Select sid from sc where cid in (select cid from course where tid = (select tid from teacher where tname = ‘张三’)));

7.  查询没有学全所有课程的同学的信息

Select *from student where sid in ( select sid from sc group by sid having count(cid) < (select count(cid) from course));

8.  查询至少有一门课与学号为" 01 "的同学所学相同的同学的信息

Select distinct a.* from student a left join sc b on a.sid = b.sid where b.cid in (select cid from sc where sid ='01');

9.  查询和" 01 "号的同学学习的课程 完全相同的其他同学的信息

Select a.* from student a left join (select * from sc where sid not in (select sid from sc  where cid not in (select cid from sc where sid = '01')) and sid != '01') b on a.sid = b.sid group by a.sid having count(b.cid) = (select count(*) from sc where sid = '01') ;

10.  查询没学过"张三"老师讲授的任一门课程的学生姓名

Select * from student where sid not in (select sid from sc where cid in (select cid from teacher  where tid = (select tid from teacher where tname = '张三')));

11. 查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

Select a.sid,a.sname,b.avg_score from student a inner join

(Select sid,avg(score) avg_score  from sc group by sid having count(cid) >= 2 and avg(score) < 60) b  on a.sid = b.sid ;

12. 检索" 01 "课程分数小于 60，按分数降序排列的学生信息

Select a.* from student a right join (select sid from sc where cid = '01' and score < 60 order by score desc ) b on a.sid = b.sid;

13.按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

Select * from sc a right join (select sid, avg(score) avg_score from sc group by sid ) b on a.sid = b.sid order by b.avg_score desc;

14.查询各科成绩最高分、最低分和平均分： 以如下形式显示：课程 ID，课程 name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率 及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90 要求输出课程号和选修人数，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 a.*,b.cname from

(select cid,

Max(score) as 最高分,

Min(score) as 最低分,

AVG(score) as 平均分,

Count(1) as 选修人数,

Sum(case when score>= 60 then 1 else 0 end) /count(1) as 及格率,

Sum(case when score>= 70 and score< 80 then 1 else 0 end) / count(1) as 中等率,

Sum(case when score>= 80 and score< 90 then 1 else 0 end) /count(1) as 优良率,

Sum(case when score>= 90 then 1 else 0 end) /count(1) as 优秀率

from sc group by cid

) a left join course b on a.cid = b.cid order by 选修人数 DESC, a.cid ASC;

15. 按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺

select  a.sid,a.cid,a.score from sc a  left join sc b  on a.cid=b.cid  and a.score<b.score group by a.cid,a.sid order by a.cid,a.score;

16查询学生的总成绩，并进行排名，总分重复时保留名次空缺

Select a.*,sum(b.score) b_score from student a left join sc b on a.sid = b.sid group by b.sid order by b_score desc;

16.1 按各科成绩进行排序，并显示排名， Score 重复时合并名次

Select

a.sid,a.cid,a.score

From sc a left join sc b on a.cid = b.cid and a.score < b.score group by a.cid,a.sid order by a.cid,a.score desc;

17.统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比

Select

a.cid,b.cname,

sum(case when a.score <= 100 and a.score > 85 then 1 else 0 end) / count(1) as ‘[100,85]’, sum(case when a.score <= 85 and a.score > 70 then 1 else 0 end) / count(1) as ‘[85,70]’, sum(case when a.score <= 70 and a.score >= 60 then 1 else 0 end) / count(1) as ‘[70,60]’,

sum(case when a.score < 60 and a.score >= 0 then 1 else 0 end) / count(1) as ‘[60,0]’  

From sc a left join course b on a.cid = b.cid group by a.cid;

18查询各科成绩前三名的记录

Select a.*

From sc a left join sc b on a.cid = b.cid and a.score < b.score group by a.cid,a.sid having count(a.score < b.score) < 3;

19查询每门课程被选修的学生数

Select cid,count(1) studentNumber from sc group by cid;

20. 查询出只选修两门课程的学生学号和姓名

Select a.sid,a.sname

From student a left join sc b on a.sid = b.sid group by b.sid having count(b.cid) = 2;

21. 查询男生、女生人数

Select

Sum(case when ssex='男' then 1 else 0 end),

Sum(case when ssex='女' then 1 else 0 end)

From student;

22. 查询名字中含有「风」字的学生信息

select *from student where sname like'%风%';

23. 查询同名同性学生名单，并统计同名人数

select sname,ssex,count(1) from student group by sname having count(sname) > 1;

24. 查询 1990 年出生的学生名单

select *from student where year(sage) = '1990';

25. 查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

select cid,avg(score) avg_score from sc group by cid order by avg_score desc,cid;

26. 查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩

select a.*,avg(b.score) avg_score

from student a left join sc b on a.sid = b.sid group by b.sid,a.sid having  avg_score >= 85 order by avg_score ;

27. 查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

select a.sname,b.score

from student a inner join sc  b on a.sid = b.sid and b.cid = (select cid from course where cname='数学')  having b.score < 60;

28. 查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

select a.*,b.cid,b.score

from student a left join sc b on a.sid = b.sid;

29.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 b.sname,c.cname,a.score

from sc a left join student b on a.sid = b.sid left join course c on a.cid = c.cid where a.score > 70;

30. 查询不及格的课程

select *from sc where score < 60;

31. 查询课程编号为 01 且课程成绩在 80 分以上的学生的学号和姓名

select b.sid,b.sname,a.score

from sc a left join student b on a.sid = b.sid where a.score >= 80 and a.cid='01';

32. 求每门课程的学生人数

select cid,count(1) from sc group by cid;

33. 成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

select a.*,b.score

from student a inner join sc b on a.sid = b.sid

inner join course c on b.cid = c.cid

inner join teacher d on d.tid = c.tid

where d.tname='张三'

order by b.score desc

limit 1;

34. 成绩有重复的情况下，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

select student.*,a.score

from sc a left join sc b on a.cid = b.cid and a.score < b.score

 inner join course on a.cid = course.cid

 inner join teacher on course.tid = teacher.tid and teacher.tname = '张三'

 inner join student on a.sid = student.sid

group by a.cid,a.sid

having count(a.score < b.score) = 0;

35. 查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩（Mysql版本太低，无法使用窗口函数，略）

36. 查询每门功成绩最好的前两名（Mysql版本太低，无法使用窗口函数，略）

37.统计每门课程的学生选修人数（超过 5 人的课程才统计）。

Select cid,count(1) from sc group by cid having count(1) > 5;

38. 检索至少选修两门课程的学生学号

select sid,count(1)

from sc group by sid having count(1) >1;

39. 查询选修了全部课程的学生信息

select * from student where sid in (select sid from sc group by sid having count(1) = (select count(1) from course));

40. 查询各学生的年龄，只按年份来算

select *,year (now()) - year(sage) 年龄 from student;

41. 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一

select *, TIMESTAMPDIFF(YEAR,sage,NOW()) as 年龄 from Student;

42. 查询本周过生日的学生

Select sid,week(sage),week(now()) from student where week(sage) = week(now());

43. 查询下周过生日的学生

Select sid,week(sage),week(now()) from student where week(sage) = week(now()) + 1;

44. 查询本月过生日的学生
select sid,month(sage),month(now()) from student where month(sage) = month(now()) ;

45. 查询下月过生日的学生

select sid,month(sage),month(now()) from student where month(sage) = month(now()) + 1 ;