[转载]SQL语句练习
时间：2021-07-01 10:21:17
帮助过：5人阅读
、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
思路：
获取所有有生物课程的人（学号，成绩） - 临时表
获取所有有物理课程的人（学号，成绩） - 临时表
根据【学号】连接两个临时表：
学号 物理成绩 生物成绩
然后再进行筛选
select A.student_id,sw,ty
from
(select student_id,num
as sw
from score
left join course
on score.course_id
= course.cid
where course.cname
= ‘生物‘)
as A
left join
(select student_id,num
as ty
from score
left join course
on score.course_id
= course.cid
where course.cname
= ‘体育‘)
as B
on A.student_id
= B.student_id
where sw
> if(
isnull(ty),
0,ty);
3、查询平均成绩大于60分的同学的学号和平均成绩；
思路：
根据学生分组，使用avg获取平均值，通过having对avg进行筛选
select student_id,
avg(num)
from score
group by student_id
having avg(num)
> 60
4、查询所有同学的学号、姓名、选课数、总成绩；
select score.student_id,
sum(score.num),
count(score.student_id),student.sname
from
score left join student
on score.student_id
= student.sid
group by score.student_id
5、查询姓“李”的老师的个数；
select count(tid)
from teacher
where tname
like ‘李%‘
select count(
1)
from (
select tid
from teacher
where tname
like ‘李%‘)
as B
6、查询没学过“叶平”老师课的同学的学号、姓名；
思路：
先查到“李平老师”老师教的所有课ID
获取选过课的所有学生ID
学生表中筛选
select * from student
where sid
not in (
select DISTINCT student_id
from score
where score.course_id
in (
select cid
from course
left join teacher
on course.teacher_id
= teacher.tid
where tname
= ‘李平老师‘
)
)
7、查询学过“
001”并且也学过编号“
002”课程的同学的学号、姓名；
思路：
先查到既选择001又选择002课程的所有同学
根据学生进行分组，如果学生数量等于2表示，两门均已选择
select student_id,sname
from
(select student_id,course_id
from score
where course_id
= 1 or course_id
= 2)
as B
left join student
on B.student_id
= student.sid
group by student_id
HAVING count(student_id)
> 1
8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
同上，只不过将001和002变成 in (叶平老师的所有课)
9、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；
同第1题
10、查询有课程成绩小于60分的同学的学号、姓名；
select sid,sname
from student
where sid
in (
select distinct student_id
from score
where num
< 60
)
11、查询没有学全所有课的同学的学号、姓名；
思路：
在分数表中根据学生进行分组，获取每一个学生选课数量
如果数量 == 总课程数量，表示已经选择了所有课程
select student_id,sname
from score
left join student
on score.student_id
= student.sid
group by student_id
HAVING count(course_id)
= (
select count(
1)
from course)
12、查询至少有一门课与学号为“
001”的同学所学相同的同学的学号和姓名；
思路：
获取 001 同学选择的所有课程
获取课程在其中的所有人以及所有课程
根据学生筛选，获取所有学生信息
再与学生表连接，获取姓名
select student_id,sname,
count(course_id)
from score
left join student
on score.student_id
= student.sid
where student_id
!= 1 and course_id
in (
select course_id
from score
where student_id
= 1)
group by student_id
13、查询至少学过学号为“
001”同学所有课的其他同学学号和姓名；
先找到和001的学过的所有人
然后个数 ＝ 001所有学科 ＝＝》 其他人可能选择的更多
select student_id,sname,
count(course_id)
from score
left join student
on score.student_id
= student.sid
where student_id
!= 1 and course_id
in (
select course_id
from score
where student_id
= 1)
group by student_id
having count(course_id) ＝ (
select count(course_id)
from score
where student_id
= 1)
14、查询和“
002”号的同学学习的课程完全相同的其他同学学号和姓名；
个数相同
002学过的也学过
select student_id,sname
from score
left join student
on score.student_id
= student.sid
where student_id
in (
select student_id
from score
where student_id
!= 1 group by student_id
HAVING count(course_id)
= (
select count(
1)
from score
where student_id
= 1)
) and course_id
in (
select course_id
from score
where student_id
= 1)
group by student_id
HAVING count(course_id)
= (
select count(
1)
from score
where student_id
= 1)
15、删除学习“叶平”老师课的score表记录；
delete from score
where course_id
in (
select cid
from course
left join teacher
on course.teacher_id
= teacher.tid
where teacher.name
= ‘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：①没有上过编号“
002”课程的同学学号；②插入“
002”号课程的平均成绩；
思路：
由于insert 支持
inset into tb1(xx,xx)
select x1,x2
from tb2;
所有，获取所有没上过002课的所有人，获取002的平均成绩
insert into score(student_id, course_id, num)
select sid,
2,(
select avg(num)
from score
where course_id
= 2)
from student
where sid
not in (
select student_id
from score
where course_id
= 2
)
17、按平均成绩从低到高 显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，按如下形式显示： 学生ID,语文,数学,英语,有效课程数,有效平均分；
select sc.student_id,
(select num
from score
left join course
on score.course_id
= course.cid
where course.cname
= "生物"
and score.student_id
=sc.student_id)
as sy,
(select num
from score
left join course
on score.course_id
= course.cid
where course.cname
= "物理"
and score.student_id
=sc.student_id)
as wl,
(select num
from score
left join course
on score.course_id
= course.cid
where course.cname
= "体育"
and score.student_id
=sc.student_id)
as ty,
count(sc.course_id),
avg(sc.num)
from score
as sc
group by student_id
desc
18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分；
select course_id,
max(num)
as max_num,
min(num)
as min_num
from score
group by course_id;
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；
思路：case when ..
then
select course_id,
avg(num)
as avgnum,
sum(
case when score.num
> 60 then 1 else 0 END)
/count(
1)
*100 as percent from score
group by course_id
order by avgnum
asc,
percent desc;
20、课程平均分从高到低显示（现实任课老师）；
select avg(
if(
isnull(score.num),
0,score.num)),teacher.tname
from course
left join score
on course.cid
= score.course_id
left join teacher
on course.teacher_id
= teacher.tid
group by score.course_id
21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
select score.sid,score.course_id,score.num,T.first_num,T.second_num
from score
left join
(
select
sid,
(select num
from score
as s2
where s2.course_id
= s1.course_id
order by num
desc limit
0,
1)
as first_num,
(select num
from score
as s2
where s2.course_id
= s1.course_id
order by num
desc limit
3,
1)
as second_num
from
score as s1
) as T
on score.sid
=T.sid
where score.num
<= T.first_num
and score.num
>= T.second_num
22、查询每门课程被选修的学生数；
select course_id,
count(
1)
from score
group by course_id;
23、查询出只选修了一门课程的全部学生的学号和姓名；
select student.sid, student.sname,
count(
1)
from score
left join student
on score.student_id
= student.sid
group by course_id
having count(
1)
= 1
24、查询男生、女生的人数；
select * from
(select count(
1)
as man
from student
where gender
=‘男‘)
as A ,
(select count(
1)
as feman
from student
where gender
=‘女‘)
as B
25、查询姓“张”的学生名单；
select sname
from student
where sname
like ‘张%‘;
26、查询同名同姓学生名单，并统计同名人数；
select sname,
count(
1)
as count from student
group by sname;
27、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列；
select course_id,
avg(
if(
isnull(num),
0 ,num))
as avg from score
group by course_id
order by avg asc,course_id
desc;
28、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 student_id,sname,
avg(
if(
isnull(num),
0 ,num))
from score
left join student
on score.student_id
= student.sid
group by student_id;
29、查询课程名称为“数学”，且分数低于60的学生姓名和分数；
select student.sname,score.num
from score
left join course
on score.course_id
= course.cid
left join student
on score.student_id
= student.sid
where score.num
< 60 and course.cname
= ‘生物‘
30、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 * from score
where score.student_id
= 3 and score.num
> 80
31、求选了课程的学生人数
select count(
distinct student_id)
from score
select count(c)
from (
select count(student_id)
as c
from score
group by student_id)
as A
32、查询选修“杨艳”老师所授课程的学生中，成绩最高的学生姓名及其成绩；
select sname,num
from score
left join student
on score.student_id
= student.sid
where score.course_id
in (
select course.cid
from course
left join teacher
on course.teacher_id
= teacher.tid
where tname
=‘张磊老师‘)
order by num
desc limit
1;
33、查询各个课程及相应的选修人数；
select course.cname,
count(
1)
from score
left join course
on score.course_id
= course.cid
group by course_id;
34、查询不同课程但成绩相同的学生的学号、课程号、学生成绩；
select DISTINCT s1.course_id,s2.course_id,s1.num,s2.num
from score
as s1, score
as s2
where s1.num
= s2.num
and s1.course_id
!= s2.course_id;
35、查询每门课程成绩最好的前两名；
select score.sid,score.course_id,score.num,T.first_num,T.second_num
from score
left join
(
select
sid,
(select num
from score
as s2
where s2.course_id
= s1.course_id
order by num
desc limit
0,
1)
as first_num,
(select num
from score
as s2
where s2.course_id
= s1.course_id
order by num
desc limit
1,
1)
as second_num
from
score as s1
) as T
on score.sid
=T.sid
where score.num
<= T.first_num
and score.num
>= T.second_num
36、检索至少选修两门课程的学生学号；
select student_id
from score
group by student_id
having count(student_id)
> 1
37、查询全部学生都选修的课程的课程号和课程名；
select course_id,
count(
1)
from score
group by course_id
having count(
1)
= (
select count(
1)
from student);
38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；
select student_id,student.sname
from score
left join student
on score.student_id
= student.sid
where score.course_id
not in (
select cid
from course
left join teacher
on course.teacher_id
= teacher.tid
where tname
= ‘张磊老师‘
)
group by student_id
39、查询两门以上不及格课程的同学的学号及其平均成绩；
select student_id,
count(
1)
from score
where num
< 60 group by student_id
having count(
1)
> 2
40、检索“
004”课程分数小于60，按分数降序排列的同学学号；
select student_id
from score
where num
< 60 and course_id
= 4 order by num
desc;
41、删除“
002”同学的“
001”课程的成绩；
delete from score
where course_id
= 1 and student_id
= 2
[转载]SQL语句练习
标签：and 顺序 信息 连接 into insert man font else
