MySQL习题
时间：2021-07-01 10:21:17
帮助过：9人阅读
2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
2 思路：
3 获取所有有生物课程的人（学号，成绩）
- 临时表
4 获取所有有物理课程的人（学号，成绩）
- 临时表
5 根据【学号】连接两个临时表：
6 学号 物理成绩 生物成绩
7
8 然后再进行筛选
9
10 select A.student_id,sw,ty
from
11
12 (
select student_id,num
as sw
from score
left join course
on score.course_id
= course.cid
where course.cname
= ‘生物‘)
as A
13
14 left join
15
16 (
select student_id,num
as ty
from score
left join course
on score.course_id
= course.cid
where course.cname
= ‘体育‘)
as B
17
18 on A.student_id
= B.student_id
where sw
> if(
isnull(ty),
0,ty);
19
20 3、查询平均成绩大于60分的同学的学号和平均成绩；
21 思路：
22 根据学生分组，使用avg获取平均值，通过having对avg进行筛选
23
24 select student_id,
avg(num)
from score
group by student_id
having avg(num)
> 60
25
26 4、查询所有同学的学号、姓名、选课数、总成绩；
27
28 select score.student_id,
sum(score.num),
count(score.student_id),student.sname
29 from
30 score
left join student
on score.student_id
= student.sid
31 group by score.student_id
32
33 5、查询姓“李”的老师的个数；
34 select count(tid)
from teacher
where tname
like ‘李%‘
35
36 select count(
1)
from (
select tid
from teacher
where tname
like ‘李%‘)
as B
37
38 6、查询没学过“叶平”老师课的同学的学号、姓名；
39 思路：
40 先查到“李平老师”老师教的所有课ID
41 获取选过课的所有学生ID
42 学生表中筛选
43 select * from student
where sid
not in (
44 select DISTINCT student_id
from score
where score.course_id
in (
45 select cid
from course
left join teacher
on course.teacher_id
= teacher.tid
where tname
= ‘李平老师‘
46 )
47 )
48
49 7、查询学过“
001”并且也学过编号“
002”课程的同学的学号、姓名；
50 思路：
51 先查到既选择001又选择002课程的所有同学
52 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
53
54 select student_id,sname
from
55
56 (
select student_id,course_id
from score
where course_id
= 1 or course_id
= 2)
as B
57
58 left join student
on B.student_id
= student.sid
group by student_id
HAVING count(student_id)
> 1
59
60
61 8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
62
63 同上，只不过将001和002变成
in (叶平老师的所有课)
64
65 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；
66 同第1题
67
68
69 10、查询有课程成绩小于60分的同学的学号、姓名；
70
71 select sid,sname
from student
where sid
in (
72 select distinct student_id
from score
where num
< 60
73 )
74
75 11、查询没有学全所有课的同学的学号、姓名；
76 思路：
77 在分数表中根据学生进行分组，获取每一个学生选课数量
78 如果数量
== 总课程数量，表示已经选择了所有课程
79
80 select student_id,sname
81 from score
left join student
on score.student_id
= student.sid
82 group by student_id
HAVING count(course_id)
= (
select count(
1)
from course)
83
84
85 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；
86 思路：
87 获取
001 同学选择的所有课程
88 获取课程在其中的所有人以及所有课程
89 根据学生筛选，获取所有学生信息
90 再与学生表连接，获取姓名
91
92 select student_id,sname,
count(course_id)
93 from score
left join student
on score.student_id
= student.sid
94 where student_id
!= 1 and course_id
in (
select course_id
from score
where student_id
= 1)
group by student_id
95
96 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；
97 先找到和001的学过的所有人
98 然后个数 ＝ 001所有学科 ＝＝》 其他人可能选择的更多
99
100 select student_id,sname,
count(course_id)
101 from score
left join student
on score.student_id
= student.sid
102 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)
103
104 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；
105
106 个数相同
107 002学过的也学过
108
109 select student_id,sname
from score
left join student
on score.student_id
= student.sid
where student_id
in (
110 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)
111 )
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)
112
113
114 15、删除学习“叶平”老师课的score表记录；
115
116 delete from score
where course_id
in (
117 select cid
from course
left join teacher
on course.teacher_id
= teacher.tid
where teacher.name
= ‘叶平‘
118 )
119
120 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；
121 思路：
122 由于insert 支持
123 inset
into tb1(xx,xx)
select x1,x2
from tb2;
124 所有，获取所有没上过002课的所有人，获取002的平均成绩
125
126 insert into score(student_id, course_id, num)
select sid,
2,(
select avg(num)
from score
where course_id
= 2)
127 from student
where sid
not in (
128 select student_id
from score
where course_id
= 2
129 )
130
131 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；
132 select sc.student_id,
133 (
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,
134 (
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,
135 (
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,
136 count(sc.course_id),
137 avg(sc.num)
138 from score
as sc
139 group by student_id
desc
140
141 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；
142
143 select course_id,
max(num)
as max_num,
min(num)
as min_num
from score
group by course_id;
144
145 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；
146 思路：
case when ..
then
147 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;
148
149 20、课程平均分从高到低显示（现实任课老师）；
150
151 select avg(
if(
isnull(score.num),
0,score.num)),teacher.tname
from course
152 left join score
on course.cid
= score.course_id
153 left join teacher
on course.teacher_id
= teacher.tid
154
155 group by score.course_id
156
157
158 21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
159 select score.sid,score.course_id,score.num,T.first_num,T.second_num
from score
left join
160 (
161 select
162 sid,
163 (
select num
from score
as s2
where s2.course_id
= s1.course_id
order by num
desc limit
0,
1)
as first_num,
164 (
select num
from score
as s2
where s2.course_id
= s1.course_id
order by num
desc limit
3,
1)
as second_num
165 from
166 score
as s1
167 )
as T
168 on score.sid
=T.sid
169 where score.num
<= T.first_num
and score.num
>= T.second_num
170
171 22、查询每门课程被选修的学生数；
172
173 select course_id,
count(
1)
from score
group by course_id;
174
175 23、查询出只选修了一门课程的全部学生的学号和姓名；
176 select student.sid, student.sname,
count(
1)
from score
177
178 left join student
on score.student_id
= student.sid
179
180 group by course_id
having count(
1)
= 1
181
182
183 24、查询男生、女生的人数；
184 select * from
185 (
select count(
1)
as man
from student
where gender
=‘男‘)
as A ,
186 (
select count(
1)
as feman
from student
where gender
=‘女‘)
as B
187
188 25、查询姓“张”的学生名单；
189 select sname
from student
where sname
like ‘张%‘;
190
191 26、查询同名同姓学生名单，并统计同名人数；
192
193 select sname,
count(
1)
as count from student
group by sname;
194
195 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；
196 select course_id,
avg(
if(
isnull(num),
0 ,num))
as avg from score
group by course_id
order by avg asc,course_id
desc;
197
198 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；
199
200 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;
201
202 29、查询课程名称为“数学”，且分数低于60的学生姓名和分数；
203
204 select student.sname,score.num
from score
205 left join course
on score.course_id
= course.cid
206 left join student
on score.student_id
= student.sid
207 where score.num
< 60 and course.cname
= ‘生物‘
208
209 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；
210 select * from score
where score.student_id
= 3 and score.num
> 80
211
212 31、求选了课程的学生人数
213
214 select count(
distinct student_id)
from score
215
216 select count(c)
from (
217 select count(student_id)
as c
from score
group by student_id)
as A
218
219 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；
220
221 select sname,num
from score
222 left join student
on score.student_id
= student.sid
223 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;
224
225 33、查询各个课程及相应的选修人数；
226 select course.cname,
count(
1)
from score
227 left join course
on score.course_id
= course.cid
228 group by course_id;
229
230
231 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；
232 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;
233
234 35、查询每门课程成绩最好的前两名；
235
236 select score.sid,score.course_id,score.num,T.first_num,T.second_num
from score
left join
237 (
238 select
239 sid,
240 (
select num
from score
as s2
where s2.course_id
= s1.course_id
order by num
desc limit
0,
1)
as first_num,
241 (
select num
from score
as s2
where s2.course_id
= s1.course_id
order by num
desc limit
1,
1)
as second_num
242 from
243 score
as s1
244 )
as T
245 on score.sid
=T.sid
246 where score.num
<= T.first_num
and score.num
>= T.second_num
247
248 36、检索至少选修两门课程的学生学号；
249 select student_id
from score
group by student_id
having count(student_id)
> 1
250
251 37、查询全部学生都选修的课程的课程号和课程名；
252 select course_id,
count(
1)
from score
group by course_id
having count(
1)
= (
select count(
1)
from student);
253
254 38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；
255 select student_id,student.sname
from score
256 left join student
on score.student_id
= student.sid
257 where score.course_id
not in (
258 select cid
from course
left join teacher
on course.teacher_id
= teacher.tid
where tname
= ‘张磊老师‘
259 )
260 group by student_id
261
262 39、查询两门以上不及格课程的同学的学号及其平均成绩；
263
264 select student_id,
count(
1)
from score
where num
< 60 group by student_id
having count(
1)
> 2
265
266 40、检索“
004”课程分数小于60，按分数降序排列的同学学号；
267 select student_id
from score
where num
< 60 and course_id
= 4 order by num
desc;
268
269 41、删除“
002”同学的“
001”课程的成绩；
270 delete from score
where course_id
= 1 and student_id
= 2
MySQL习题
标签：let 表连接 like max 名称 大于 筛选 生成 font
