最全50个Mysql数据库查询练习题
此数据库查询语句是网络上50个数据库查询练习题目,网上有些版本是oracle语句写的,大多数公司还是用免费的mysql数据库,以下都是mysql版本,全部都有验证过。
表名和字段
–1.学生表
student(s#, sname, sage,ssex) –学生编号,学生姓名, 出生年月,学生性别
–2.课程表
course(c#,cname,t#) – –课程编号, 课程名称, 教师编号
–3.教师表
teacher(t#,tname) –教师编号,教师姓名
–4.成绩表
sc(s#,c#,score) –学生编号,课程编号,分数
测试数据
用数据库可视化工具做练习非常方便,推荐使用sqlyog,软件图标是一只海豚。
在新连接种填上本机地址,用户名,密码和端口就直接连上mysql。
所有测试数据如下:
# --插入学生表测试数据 insert into student values('01' , '赵雷' , '1990-01-01' , '男'); insert into student values('02' , '钱电' , '1990-12-21' , '男'); insert into student values('03' , '孙风' , '1990-05-20' , '男'); insert into student values('04' , '李云' , '1990-08-06' , '男'); insert into student values('05' , '周梅' , '1991-12-01' , '女'); insert into student values('06' , '吴兰' , '1992-03-01' , '女'); insert into student values('07' , '郑竹' , '1989-07-01' , '女'); insert into student values('08' , '王菊' , '1990-01-20' , '女'); # --插入课程表测试数据 insert into course values('01' , '语文' , '02'); insert into course values('02' , '数学' , '01'); insert into course values('03' , '英语' , '03'); # --插入教师表测试数据 insert into teacher values('01' , '张三'); insert into teacher values('02' , '李四'); insert into teacher values('03' , '王五'); # --插入成绩表测试数据 insert into sc values('01' , '01' , 80); insert into sc values('01' , '02' , 90); insert into sc values('01' , '03' , 99); insert into sc values('02' , '01' , 70); insert into sc values('02' , '02' , 60); insert into sc values('02' , '03' , 80); insert into sc values('03' , '01' , 80); insert into sc values('03' , '02' , 80); insert into sc values('03' , '03' , 80); insert into sc values('04' , '01' , 50); insert into sc values('04' , '02' , 30); insert into sc values('04' , '03' , 20); insert into sc values('05' , '01' , 76); insert into sc values('05' , '02' , 87); insert into sc values('06' , '01' , 31); insert into sc values('06' , '03' , 34); insert into sc values('07' , '02' , 89); insert into sc values('07' , '03' , 98);
最后是50个数据库查询练习,已经验证过,是mysql版本的。
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 `s#` as sno1, `c#`as cno1, score from sc where `c#`=01) a left join (select `s#` as sno2, `c#`as cno2, score from sc where `c#`=02) b on a.sno1 = b.sno2 where a.score > b.score
1.1 查询同时存在" 01 "课程和" 02 "课程的情况
select * from (select `s#` as sno1, `c#`as cno1, score from sc where `c#`=01) a left join (select `s#` as sno2, `c#`as cno2, score from sc where `c#`=02) b on a.sno1 = b.sno2 where sno2 is not null
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 `s#` as sno1, `c#`as cno1, score from sc where `c#`=01) a left join (select `s#` as sno2, `c#`as cno2, score from sc where `c#`=02) b on a.sno1 = b.sno2
1.3 查询不存在" 01 "课程但存在" 02 "课程的情况
select * from
sc where `c#`='02' and `s#` not in (select `s#` from sc where `c#`='01')
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.`s#`,b.`sname`, a.avg_score from (select `s#` ,avg(score) as avg_score from sc group by `s#`) as a left join student as b on a.`s#` = b.`s#` where a.avg_score >=60
3. 查询在 sc 表存在成绩的学生信息
select * from student where `s#` in (select distinct `s#` 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 `s#` ,sname , course_num , score_sum from (select `s#`, sname from student ) as a left join (select `s#` as sno ,count(`c#`) as course_num ,sum(score) as score_sum from sc group by sno) as b on a.`s#` = b.sno
4.1 查有成绩的学生信息
# 在最外面一层select的时候,不可以用函数
# 如果两张表连接之后,有相同的字段,这时候select就需要把其中一个字段改名
select `s#` ,sname , course_num , score_sum from (select `s#`, sname from student ) as a left join (select `s#` as sno ,count(`c#`) as course_num ,sum(score) as score_sum from sc group by sno) as b on a.`s#` = b.sno where course_num is not null
5. 查询「李」姓老师的数量
select count(*) from teacher where tname like '李%'
6. 查询学过「张三」老师授课的同学的信息
# 张三老师是01号 select * from student where `s#` in (select `s#` from sc where `c#` = (select `c#` from course where `t#` = (select `t#` from teacher where tname='张三')))
# 7. 查询没有学全所有课程的同学的信息
select `s#`,count(`c#`) as course_num from sc group by `s#`
having course_num < (select count(*) 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 * from student where `s#` in (select distinct `s#` from sc where `c#` in (select `c#` from sc where `s#`=01)) and `s#`!= 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 `s#` from (select * from sc left join (select `c#` as cno from sc where `s#` =01) a on sc.`c#` = a.cno) as b group by `s#` having count(b.`s#`) = (select count(`c#`) as cno from sc where `s#` =01)
# 10. 查询没学过"张三"老师讲授的任一门课程的学生姓名
# 张三是01 # 01老师是教数学,c#是02 select * from student where `s#` not in (select distinct `s#` from sc where `c#` in (select `c#` from course where `t#` in (select `t#` 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 `s#`, sname, avg_score from (select `s#`, sname from student where `s#` in (select a.`s#` from (select `s#`,count(`c#`) as num from sc where score <60 group by `s#`) a where num >=2)) as b left join (select `s#` as sno ,avg(score) as avg_score from sc group by `s#`) as c on b.`s#` = c.sno
# 12. 检索" 01 "课程分数小于 60,按分数降序排列的学生信息
select `s#`, sname, score from student as a left join (select `s#` as sno,`c#`,score from sc where `c#`= 01 and score <60 )b on a.`s#`= b.sno where score is not null order by score desc
# 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 `s#` ,avg(score) as avg_score from sc group by `s#` order by 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 distinct a.`c#`,cname,最高分,最低分,平均分,及格率,中等率,优良率,优秀率 from sc a left join course on a.`c#`=course.`c#` left join (select `c#`, max(score)最高分, min(score)最低分, avg(score)平均分 from sc group by `c#`)b on a.`c#`=b.`c#` left join (select `c#`, round( r1 /cnt * 100, 2 ) as 及格率 from (select `c#`, (sum(case when score >=60 then 1 else 0 end)*1.00) as r1 , count(*) as cnt from sc group by `c#`) c1) c on a.`c#`=c.`c#` left join (select `c#`, round( r2 /cnt * 100, 2 ) as 中等率 from (select `c#`, (sum(case when score >=70 and score<80 then 1 else 0 end)*1.00) as r2 , count(*) as cnt from sc group by `c#`) d1) d on a.`c#`=d.`c#` left join (select `c#`, round( r3 /cnt * 100, 2 ) as 优良率 from (select `c#`, (sum(case when score >=80 and score<90 then 1 else 0 end)*1.00) as r3 , count(*) as cnt from sc group by `c#`) e1) e on a.`c#`=e.`c#` left join (select `c#`, round( r4 /cnt * 100, 2 ) as 优秀率 from (select `c#`, (sum(case when score >=90 then 1 else 0 end)*1.00) as r4 , count(*) as cnt from sc group by `c#`) f1) f on a.`c#`=f.`c#`
# 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
# mysql中没有rank()函数 # 这种是重复时候保留名次,所以最后名次和人数是一样的 select `s#`, `c#`, score, rank from (select `s#`, `c#`, score, @currank := if(@prevrank = score, @currank, @incrank) as rank, @incrank := @incrank + 1, @prevrank := score from sc , ( select @currank :=0, @prevrank := null, @incrank := 1 ) r order by score desc) s
# 15.1 按各科成绩进行排序,并显示排名, score 重复时合并名次
# 这种是当有重复名次的时候变成只有一个名次,所以排名的数量会变少 select `s#`, `c#`, score, case when @prevrank = score then @currank when @prevrank := score then @currank := @currank + 1 end as rank from sc, (select @currank :=0, @prevrank := null) r order by score desc
# 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
# from后面不需要加表的别名 select `s#`, sum_score, rank from (select `s#`, sum_score, @currank := if(@prevrank = sum_score, @currank, @incrank) as rank, @incrank := @incrank + 1, @prevrank := sum_score from (select `s#`, sum(score) as sum_score from sc group by `s#`) c , (select @currank :=0, @prevrank := null, @incrank := 1) r order by sum_score desc) s
# 16.1 查询学生的总成绩,并进行排名,总分重复时不保留名次空缺
select c.*, case when @prevrank = c.sum_score then @currank when @prevrank := c.sum_score then @currank := @currank + 1 end as rank from (select a.`s#`,a.sname,sum(score) as sum_score from (student as a right join sc as b on a.`s#` = b.`s#`) group by a.`s#` ) c , (select @currank := 0 , @prevrank :=null ) d order by sum_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.`c#` , b.cname, sum(case when score >=85 and score <=100 then 1 else 0 end ) '[100-85]', sum(case when score >=85 and score <=100 then 1 else 0 end )*1.00/count(*) as '[100-85]percent', sum(case when score < 85 and score >= 70 then 1 else 0 end ) '(85-70]', sum(case when score < 85 and score >= 70 then 1 else 0 end )*1.00/count(*) as '(85-70]percent', sum(case when score < 70 and score >= 60 then 1 else 0 end ) '(70-60]', sum(case when score < 70 and score >= 60 then 1 else 0 end )*1.00/count(*) as '(85-70]percent', sum(case when score < 60 and score >= 0 then 1 else 0 end ) '(60-0]', sum(case when score < 60 and score >= 0 then 1 else 0 end )*1.00/count(*) as '(85-70]percent', count(*) as counts from sc a left join course b on a.`c#` = b.`c#` group by `c#`
# 18. 查询各科成绩前三名的记录
select * from sc a where (select count(*) from sc where `c#`=a.`c#` and score>a.score)<3 order by a.`c#`, a.score desc;
# 19. 查询每门课程被选修的学生数
select `c#`, count(`s#`) from (select `s#`,`c#` from sc order by `c#`)a group by `c#` select a.`c#` , b.cname ,count(*) as num from sc a left join course b on a.`c#` = b.`c#` group by a.`c#`;
# 20. 查询出只选修两门课程的学生学号和姓名
select a.`s#`, a.sname ,cnt from student a left join (select `s#`,count(`c#`) as cnt from sc group by `s#`) b on a.`s#`=b.`s#` where cnt=2
# 21. 查询男生、女生人数
select ssex,count(ssex) from student group by ssex
# 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 a.*,b.同名人数 from student a left join (select sname,ssex,count(*) as 同名人数 from student group by sname,ssex)b on a.sname=b.sname and a.ssex=b.ssex where b.同名人数>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 `c#`, round(avg(score),2) as avg_score from sc group by `c#` order by `c#` asc
# 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 c.`s#`,sname ,avg_score from (student c left join (select `s#`, avg_score from (select `s#` ,round(avg(score),2) as avg_score from sc group by `s#` order by avg_score desc)a where avg_score >=85) b on c.`s#` =b.`s#`) where avg_score is not null
# 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.`s#`,a.sname,b.math, b.score from student a left join (select `s#`,`c#` as math ,score from sc where `c#` in (select `c#` from course where cname = '数学') and sc.score <60) b on a.`s#`=b.`s#` where b.score is not null
# 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.`s#`,a.`sname`,a.`sage`,a.`ssex`,b.`c#`,b.score from student a left join sc b on a.`s#` = b.`s#` left join course c on c.`c#` = b.`c#`
# 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 a.`s#`,a.`sname`,a.`sage`,a.`ssex`,b.`c#`,b.score from student a left join (select `s#`,`c#`,score from sc where score >70) b on a.`s#`=b.`s#` left join course c on c.`c#`=b.`c#` where score is not null
# 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 a.`s#`, a.sname ,b.score from student a left join (select * from sc where `c#`='01' and score >= 80) b on a.`s#` = b.`s#` where score is not null
# 32. 求每门课程的学生人数
select `c#`,count(`c#`) from sc group by `c#`
# 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.`s#`, a.`sname` ,b.`c#`, b.max_score from student a left join (select `s#` as sid,`c#` ,max(score) as max_score from sc where `c#` in (select `c#` from course where `t#` in (select `t#` from teacher where tname = '张三'))) b on a.`s#`=b.sid where max_score is not null
# 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 * from (select dd.*, case when @prevrank = dd.score then @currank when @prevrank := dd.score then @currank := @currank + 1 end as rank from (select a.*,b.score from student a left join sc b on a.`s#` = b.`s#` left join course c on b.`c#` = c.`c#` left join teacher d on c.`t#` = d.`t#` where d.tname = '张三' ) dd,(select @currank := 0 , @prevrank :=null ) ff order by score desc) as dddddddd where rank = 1;
# 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
select distinct a.`s#`, a.`c#`, a.score from sc as a join sc as b where a.`c#` != b.`c#` and a.score = b.score and a.`s#` != b.`s#` order by a.`s#`, a.`c#`, a.score
# 36. 查询每门功课成绩最好的前两名
# 此题和18题相同 select * from sc a where (select count(*) from sc where `c#`=a.`c#` and score>a.score)<2 order by a.`c#`, a.score desc;
# 37. 统计每门课程的学生选修人数(超过 5 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,若人数相同,按课程号升序排列 select a.`c#`, count(*) as num from course a left join sc b on a.`c#` = b.`c#` group by a.`c#` having num > 5 order by num,a.`c#`
# 38. 检索至少选修两门课程的学生学号
select distinct`s#`,count(`c#`) as num from sc group by `s#` having num >=2
# 39. 查询选修了全部课程的学生信息
select * from (select `s#`,count(*) as num from sc group by `s#` ) b where num = (select count(*) from course)
# 40. 查询各学生的年龄,只按年份来算
select *, year(now()) - year(sage) as age from student
# 41. 查询本周过生日的学生
select * from (select * , week(sage), month(sage),day(sage), week(str_to_date(concat_ws(',',year(now()),month(sage),day(sage)),'%y,%m,%d')) as w from student) a where w = week(now())
# 42. 查询下周过生日的学生
select * from (select * , week(sage), month(sage),day(sage),week(now()), week(str_to_date(concat_ws(',',year(now()),month(sage),day(sage)),'%y,%m,%d')) as w from student) a where w + 2 = week(now())
# 43. 查询本月过生日的学生
select * , month(sage),month(now()) from student where month(sage) = month(now())
# 44. 查询下月过生日的学生
select * , month(sage),month(now()) from student where month(sage) = month(now()) + 1
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