MySQL查询语句的50道练习(2019.09.26进阶版)
表名和字段
–1.学生表
Student(s_id,s_name,s_birth,s_sex) –学生编号,学生姓名, 出生年月,学生性别
–2.课程表
Course(c_id,c_name,t_id) – –课程编号, 课程名称, 教师编号
–3.教师表
Teacher(t_id,t_name) –教师编号,教师姓名
–4.成绩表
Score(s_id,c_id,s_score) –学生编号,课程编号,分数
#建表 #学生表 drop table if exists student; CREATE TABLE if not exists `student`( `s_id` VARCHAR(20), `s_name` VARCHAR(20) NOT NULL DEFAULT '', `s_birth` VARCHAR(20) NOT NULL DEFAULT '', `s_sex` VARCHAR(10) NOT NULL DEFAULT '', PRIMARY KEY(`s_id`) ); #课程表 drop table if exists course; CREATE TABLE if not exists `course`( `c_id` VARCHAR(20), `c_name` VARCHAR(20) NOT NULL DEFAULT '', `t_id` VARCHAR(20) NOT NULL, PRIMARY KEY(`c_id`) ); #教师表 drop table if exists teacher; CREATE TABLE if not exists `teacher`( `t_id` VARCHAR(20), `t_name` VARCHAR(20) NOT NULL DEFAULT '', PRIMARY KEY(`t_id`) ); #成绩表 drop table if exists score; CREATE TABLE if not exists `score`( `s_id` VARCHAR(20), `c_id` VARCHAR(20), `s_score` INT(3), PRIMARY KEY(`s_id`,`c_id`) ); #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'); #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'); #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'); #成绩表测试数据 insert into score values('01' , '01' , 80); insert into score values('01' , '02' , 90); insert into score values('01' , '03' , 99); insert into score values('02' , '01' , 70); insert into score values('02' , '02' , 60); insert into score values('02' , '03' , 80); insert into score values('03' , '01' , 80); insert into score values('03' , '02' , 80); insert into score values('03' , '03' , 80); insert into score values('04' , '01' , 50); insert into score values('04' , '02' , 30); insert into score values('04' , '03' , 20); insert into score values('05' , '01' , 76); insert into score values('05' , '02' , 87); insert into score values('06' , '01' , 31); insert into score values('06' , '03' , 34); insert into score values('07' , '02' , 89); insert into score values('07' , '03' , 98);
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;
-- 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'
));
-- 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
-- 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)