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mysql练习题(一)

 

练习题和sql语句

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 a.* ,b.s_score as 01_score,c.s_score as 02_score from
student a
join score b on a.s_id=b.s_id and b.c_id=’01’
left join score c on a.s_id=c.s_id and c.c_id=’02’ or c.c_id = NULL where b.s_score>c.s_score

2、查询”01″课程比”02″课程成绩低的学生的信息及课程分数

select a.* ,b.s_score as 01_score,c.s_score as 02_score from
student a left join score b on a.s_id=b.s_id and b.c_id=’01’ or b.c_id=NULL
join score c on a.s_id=c.s_id and c.c_id=’02’ where b.s_score< c.s_score

3、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 b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from
student b
join score a on b.s_id = a.s_id
GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)>=60;

ROUND 四舍五入   avg平均

4、查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩
(包括有成绩的和无成绩的)

select b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from
student b
left join score a on b.s_id = a.s_id
GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)< 60
union
select a.s_id,a.s_name,0 as avg_score from
student a
where a.s_id not in (
select distinct s_id from score);

5、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
select a.s_id,a.s_name,count(b.c_id) as sum_course,sum(b.s_score) as sum_score from
student a
left join score b on a.s_id=b.s_id
GROUP BY a.s_id,a.s_name;

6、查询”李”姓老师的数量
select count(t_id) from teacher where t_name like ‘李%’;

7、查询学过”张三”老师授课的同学的信息
select a.* from
student a
join score b on a.s_id=b.s_id where b.c_id in(
select c_id from course where t_id =(
select t_id from teacher where t_name = ‘张三’));

8、查询没学过”张三”老师授课的同学的信息
select * from
student c
where c.s_id not in(
select a.s_id from student a join score b on a.s_id=b.s_id where b.c_id in(
select c_id from course where t_id =(
select t_id from teacher where t_name = ‘张三’)));
9、查询学过编号为”01″并且也学过编号为”02″的课程的同学的信息

select a.* from
student a,score b,score c
where a.s_id = b.s_id and a.s_id = c.s_id and b.c_id=’01’ and c.c_id=’02’;

10、查询学过编号为”01″但是没有学过编号为”02″的课程的同学的信息

select a.* from
student a
where a.s_id in (select s_id from score where c_id=’01’ ) and a.s_id not in(select s_id from score where c_id=’02’)

11、查询没有学全所有课程的同学的信息

select s.* from
student s where s.s_id in(
select s_id from score where s_id not in(
select a.s_id from score a
join score b on a.s_id = b.s_id and b.c_id=’02’
join score c on a.s_id = c.s_id and c.c_id=’03’
where a.c_id=’01’))

12、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_id in(
select distinct a.s_id from score a where a.c_id in(select a.c_id from score a where a.s_id=’01’)
);

13、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 where a.s_id in(
select distinct s_id from score where s_id!=’01’ and c_id in(select c_id from score where s_id=’01’)
group by s_id
having count(1)=(select count(1) from score where s_id=’01’));

distinct去重

14、查询没学过”张三”老师讲授的任一门课程的学生姓名
select a.s_name from student a where a.s_id not in (
select s_id from score where c_id =
(select c_id from course where t_id =(
select t_id from teacher where t_name = ‘张三’))
group by s_id);

15、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.s_id,a.s_name,ROUND(AVG(b.s_score)) from
student a
left join score b on a.s_id = b.s_id
where a.s_id in(
select s_id from score where s_score< 60 GROUP BY s_id having count(1)>=2)
GROUP BY a.s_id,a.s_name

16、检索”01″课程分数小于60,按分数降序排列的学生信息
select a.*,b.c_id,b.s_score from
student a,score b
where a.s_id = b.s_id and b.c_id=’01’ and b.s_score< 60 ORDER BY b.s_score DESC;

17、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 a.s_id,(select s_score from score where s_id=a.s_id and c_id=’01’) as 语文,
(select s_score from score where s_id=a.s_id and c_id=’02’) as 数学,
(select s_score from score where s_id=a.s_id and c_id=’03’) as 英语,
round(avg(s_score),2) as 平均分 from score a GROUP BY a.s_id ORDER BY 平均分 DESC;

18.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
select a.c_id,b.c_name,MAX(s_score),MIN(s_score),ROUND(AVG(s_score),2),
ROUND(100*(SUM(case when a.s_score>=60 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 及格率,
ROUND(100*(SUM(case when a.s_score>=70 and a.s_score<=80 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 中等率,
ROUND(100*(SUM(case when a.s_score>=80 and a.s_score<=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 优良率,
ROUND(100*(SUM(case when a.s_score>=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 优秀率
from score a left join course b on a.c_id = b.c_id GROUP BY a.c_id,b.c_name

19、按各科成绩进行排序,并显示排名(实现不完全)
mysql没有rank函数
select a.s_id,a.c_id,
@i:=@i +1 as i保留排名,
@k:=(case when @score=a.s_score then @k else @i end) as rank不保留排名,
@score:=a.s_score as score
from (
select s_id,c_id,s_score from score WHERE c_id=’01’ GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s
union
select a.s_id,a.c_id,
@i:=@i +1 as i,
@k:=(case when @score=a.s_score then @k else @i end) as rank,
@score:=a.s_score as score
from (
select s_id,c_id,s_score from score WHERE c_id=’02’ GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s
union
select a.s_id,a.c_id,
@i:=@i +1 as i,
@k:=(case when @score=a.s_score then @k else @i end) as rank,
@score:=a.s_score as score
from (
select s_id,c_id,s_score from score WHERE c_id=’03’ GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
)a,(select @k:=0,@i:=0,@score:=0)s

20、查询学生的总成绩并进行排名
select a.s_id,
@i:=@i+1 as i,
@k:=(case when @score=a.sum_score then @k else @i end) as rank,
@score:=a.sum_score as score
from (select s_id,SUM(s_score) as sum_score from score GROUP BY s_id ORDER BY sum_score DESC)a,
(select @k:=0,@i:=0,@score:=0)s

21、查询不同老师所教不同课程平均分从高到低显示

select a.t_id,c.t_name,a.c_id,ROUND(avg(s_score),2) as avg_score from course a
left join score b on a.c_id=b.c_id
left join teacher c on a.t_id=c.t_id
GROUP BY a.c_id,a.t_id,c.t_name ORDER BY avg_score DESC;
22、查询所有课程的成绩第2名到第3名的学生信息及该课程成绩

select d.*,c.排名,c.s_score,c.c_id from (
select a.s_id,a.s_score,a.c_id,@i:=@i+1 as 排名 from score a,(select @i:=0)s where a.c_id=’01’
)c
left join student d on c.s_id=d.s_id
where 排名 BETWEEN 2 AND 3
UNION
select d.*,c.排名,c.s_score,c.c_id from (
select a.s_id,a.s_score,a.c_id,@j:=@j+1 as 排名 from score a,(select @j:=0)s where a.c_id=’02’
)c
left join student d on c.s_id=d.s_id
where 排名 BETWEEN 2 AND 3
UNION
select d.*,c.排名,c.s_score,c.c_id from (
select a.s_id,a.s_score,a.c_id,@k:=@k+1 as 排名 from score a,(select @k:=0)s where a.c_id=’03’
)c
left join student d on c.s_id=d.s_id
where 排名 BETWEEN 2 AND 3;

23、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],[0-60]及所占百分比

select distinct f.c_name,a.c_id,b.85-100,b.百分比,c.70-85,c.百分比,d.60-70,d.百分比,e.0-60,e.百分比 from score a
left join (select c_id,SUM(case when s_score >85 and s_score <=100 then 1 else 0 end) as 85-100,
ROUND(100*(SUM(case when s_score >85 and s_score <=100 then 1 else 0 end)/count(*)),2) as 百分比
from score GROUP BY c_id)b on a.c_id=b.c_id
left join (select c_id,SUM(case when s_score >70 and s_score <=85 then 1 else 0 end) as 70-85,
ROUND(100*(SUM(case when s_score >70 and s_score <=85 then 1 else 0 end)/count(*)),2) as 百分比
from score GROUP BY c_id)c on a.c_id=c.c_id
left join (select c_id,SUM(case when s_score >60 and s_score <=70 then 1 else 0 end) as 60-70,
ROUND(100*(SUM(case when s_score >60 and s_score <=70 then 1 else 0 end)/count(*)),2) as 百分比
from score GROUP BY c_id)d on a.c_id=d.c_id
left join (select c_id,SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end) as 0-60,
ROUND(100*(SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end)/count(*)),2) as 百分比
from score GROUP BY c_id)e on a.c_id=e.c_id
left join course f on a.c_id = f.c_id

24、查询学生平均成绩及其名次

select a.s_id,
@i:=@i+1 as ‘不保留空缺排名’,
@k:=(case when @avg_score=a.avg_s then @k else @i end) as ‘保留空缺排名’,
@avg_score:=avg_s as ‘平均分’
from (select s_id,ROUND(AVG(s_score),2) as avg_s from score GROUP BY s_id)a,(select @avg_score:=0,@i:=0,@k:=0)b;

25、查询各科成绩前三名的记录
1.选出b表比a表成绩大的所有组
2.选出比当前id成绩大的 小于三个的
select a.s_id,a.c_id,a.s_score from score a
left join score b on a.c_id = b.c_id and a.s_score< b.s_score
group by a.s_id,a.c_id,a.s_score HAVING COUNT(b.s_id)< 3
ORDER BY a.c_id,a.s_score DESC

26、查询每门课程被选修的学生数

select c_id,count(s_id) from score a GROUP BY c_id

27、查询出只有两门课程的全部学生的学号和姓名
select s_id,s_name from student where s_id in(
select s_id from score GROUP BY s_id HAVING COUNT(c_id)=2);

28、查询男生、女生人数
select s_sex,COUNT(s_sex) as 人数 from student GROUP BY s_sex

count(s_sex)

@29、查询名字中含有”风”字的学生信息

select * from student where s_name like ‘%风%’;

30、查询同名同性学生名单,并统计同名人数

select a.s_name,a.s_sex,count(*) from student a JOIN
student b on a.s_id !=b.s_id and a.s_name = b.s_name and a.s_sex = b.s_sex
GROUP BY a.s_name,a.s_sex

@31、查询1990年出生的学生名单

select s_name from student where s_birth like ‘1990%’

32、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_id,ROUND(AVG(s_score),2) as avg_score from score GROUP BY c_id ORDER BY avg_score DESC,c_id ASC

33、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.s_id,b.s_name,ROUND(avg(a.s_score),2) as avg_score from score a
left join student b on a.s_id=b.s_id GROUP BY s_id HAVING avg_score>=85

34、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_name,b.s_score from score b LEFT JOIN student a on a.s_id=b.s_id where b.c_id=(
select c_id from course where c_name =’数学’) and b.s_score< 60

35、查询所有学生的课程及分数情况;

select a.s_id,a.s_name,
SUM(case c.c_name when ‘语文’ then b.s_score else 0 end) as ‘语文’,
SUM(case c.c_name when ‘数学’ then b.s_score else 0 end) as ‘数学’,
SUM(case c.c_name when ‘英语’ then b.s_score else 0 end) as ‘英语’,
SUM(b.s_score) as ‘总分’
from student a left join score b on a.s_id = b.s_id
left join course c on b.c_id = c.c_id
GROUP BY a.s_id,a.s_name

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 a.s_name,b.c_name,c.s_score from course b left join score c on b.c_id = c.c_id
left join student a on a.s_id=c.s_id where c.s_score>=70

37、查询不及格的课程
select a.s_id,a.c_id,b.c_name,a.s_score from score a left join course b on a.c_id = b.c_id
where a.s_score< 60

38、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_id,b.s_name from score a LEFT JOIN student b on a.s_id = b.s_id
where a.c_id = ’01’ and a.s_score>80

39、求每门课程的学生人数
select count(*) from score GROUP BY c_id;

40、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

查询老师id
select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name=’张三’

查询最高分(可能有相同分数)
select MAX(s_score) from score where c_id=’02’
查询信息
select a.*,b.s_score,b.c_id,c.c_name from student a
LEFT JOIN score b on a.s_id = b.s_id
LEFT JOIN course c on b.c_id=c.c_id
where b.c_id =(select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name=’张三’)
and b.s_score in (select MAX(s_score) from score where c_id=’02’)

41、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 b.s_id,b.c_id,b.s_score from score a,score b where a.c_id != b.c_id and a.s_score = b.s_score

42、查询每门功成绩最好的前两名
牛逼的写法
select a.s_id,a.c_id,a.s_score from score a
where (select COUNT(1) from score b where b.c_id=a.c_id and b.s_score>=a.s_score)<=2 ORDER BY a.c_id

43、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 c_id,count(*) as total from score GROUP BY c_id HAVING total>5 ORDER BY total,c_id ASC

44、检索至少选修两门课程的学生学号
select s_id,count(*) as sel from score GROUP BY s_id HAVING sel>=2

 

45、查询选修了全部课程的学生信息
select * from student where s_id in(
select s_id from score GROUP BY s_id HAVING count(*)=(select count(*) from course))

46、查询各学生的年龄
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 s_birth,(DATE_FORMAT(NOW(),’%Y’)-DATE_FORMAT(s_birth,’%Y’) –
(case when DATE_FORMAT(NOW(),’%m%d’)>DATE_FORMAT(s_birth,’%m%d’) then 0 else 1 end)) as age
from student;

47、查询本周过生日的学生
select * from student where WEEK(DATE_FORMAT(NOW(),’%Y%m%d’))=WEEK(s_birth)
select * from student where YEARWEEK(s_birth)=YEARWEEK(DATE_FORMAT(NOW(),’%Y%m%d’))

select WEEK(DATE_FORMAT(NOW(),’%Y%m%d’))

48、查询下周过生日的学生
select * from student where WEEK(DATE_FORMAT(NOW(),’%Y%m%d’))+1 =WEEK(s_birth)

49、查询本月过生日的学生

select * from student where MONTH(DATE_FORMAT(NOW(),’%Y%m%d’)) =MONTH(s_birth)

50、查询下月过生日的学生
select * from student where MONTH(DATE_FORMAT(NOW(),’%Y%m%d’))+1 =MONTH(s_birth)

 

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