建表语句
CREATE DATABASE `test2`
USE `test2`;
DROP TABLE IF EXISTS `class`;
CREATE TABLE `class` (
`cid` int(11) NOT NULL AUTO_INCREMENT,
`caption` varchar(32) NOT NULL,
PRIMARY KEY (`cid`)
)
insert into `class`(`cid`,`caption`) values (1,'三年二班'),(2,'三年三班'),(3,'一年二班')
,(4,'二年九班');
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
`cid` int(11) NOT NULL AUTO_INCREMENT,
`cname` varchar(32) NOT NULL,
`teacher_id` int(11) NOT NULL,
PRIMARY KEY (`cid`),
KEY `fk_course_teacher` (`teacher_id`),
CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`)
)
insert into `course`(`cid`,`cname`,`teacher_id`) values (1,'生物',1),(2,'物理',2),(3,'体育',3)
,(4,'美术',2);
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
`sid` int(11) NOT NULL AUTO_INCREMENT,
`student_id` int(11) NOT NULL,
`course_id` int(11) NOT NULL,
`num` int(11) NOT NULL,
PRIMARY KEY (`sid`),
KEY `fk_score_student` (`student_id`),
KEY `fk_score_course` (`course_id`),
CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`),
CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`)
)
insert into `score`(`sid`,`student_id`,`course_id`,`num`) values (1,1,1,10),(2,1,2,9),
(5,1,4,66),(6,2,1,8),(8,2,3,68),(9,2,4,99),(10,3,1,77),(11,3,2,66),(12,3,3,87),(13,3,4,99),
(14,4,1,79),(15,4,2,11),(16,4,3,67),(17,4,4,100),(18,5,1,79),(19,5,2,11),
(20,5,3,67),(21,5,4,100),(22,6,1,9),(23,6,2,100)
,(24,6,3,67),(25,6,4,100),(26,7,1,9),(27,7,2,100),(28,7,3,67)
,(29,7,4,88),(30,8,1,9),(31,8,2,100),(32,8,3,67),
(33,8,4,88),(34,9,1,91),(35,9,2,88),(36,9,3,67),(37,9,4,22)
,(38,10,1,90),(39,10,2,77),(40,10,3,43),(41,10,4,87)
,(42,11,1,90),(43,11,2,77),(44,11,3,43),(45,11,4,87),
(46,12,1,90),(47,12,2,77),(48,12,3,43),(49,12,4,87),(52,13,3,87);
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`sid` int(11) NOT NULL AUTO_INCREMENT,
`gender` char(1) NOT NULL,
`class_id` int(11) NOT NULL,
`sname` varchar(32) NOT NULL,
PRIMARY KEY (`sid`),
KEY `fk_class` (`class_id`),
CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`)
)
insert into `student`(`sid`,`gender`,`class_id`,`sname`) values (1,'男',1,'理解'),
(2,'女',1,'钢蛋'),(3,'男',1,'张三'),(4,'男',1,'张一'),(5,'女',1,'张二'),(6,'男',1,'张四'
),(7,'女',2,'铁锤'),
(8,'男',2,'李三'),(9,'男',2,'李一'),(10,'女',2,'李二'),(11,'男',2,'李四')
,(12,'女',3,'如花'),(13,'男',3,'刘三'),(14,'男',3,'刘一'),(15,'女',3,'刘二'),(16,'男',3,'刘四');
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
`tid` int(11) NOT NULL AUTO_INCREMENT,
`tname` varchar(32) NOT NULL,
PRIMARY KEY (`tid`)
)
insert into `teacher`(`tid`,`tname`) values (1,'张磊老师'),(2,'李平老师')
,(3,'刘海燕老师'),(4,'朱云海老师'),(5,'李杰老师');
1、查询所有的课程的名称以及对应的任课老师姓名
select
course.cname,
teacher.tname
from
course
inner join teacher on course.teacher_id = teacher.tid;
2、查询学生表中男女生各有多少人
select
gender,
count(1) # count(sid)
from
student
group by
gender;
3、查询物理成绩等于100的学生的姓名
select
sname
from
student
where
sid in(
select
t1.student_id
from
score t1
inner join(
select
cid
from
course
where
cname = '物理'
) t2 on t1.course_id = t2.cid
where
t1.num = 100
);
4、查询平均成绩大于八十分的同学的姓名和平均成绩
select
t1.sname,
t2.avg_num
from
student as t1
inner join(
select
student_id,
avg(num) as avg_num
from
score
group by
student_id
having
avg(num) > 80
) as t2 on t1.sid = t2.student_id;
5、查询所有学生的学号，姓名，选课数，总成绩(注意：对于那些没有选修任何课程的学生也算在内)
select
t1.sid,
t1.sname,
t2.count_course,
t2.sum_num
from
student as t1
left join(
select
student_id,
count(course_id) as count_course,
sum(num) as sum_num
from
score
group by
student_id
) as t2 on t1.sid = t2.student_id;
6、 查询姓李老师的个数
select
count(tid)
from
teacher
where
tname like '李%';
7、 查询没有报李平老师课的学生姓名
select
sname
from
student
where
sid not in(
select distinct
student_id
from
score
where
course_id in (
select
cid
from
course
inner join teacher on course.teacher_id = teacher.tid
where teacher.tname = '李平老师'
)
);
8、 查询物理课程比生物课程高的学生的学号(分别得到物理成绩表与生物成绩表，然后连表即可)
select
t1.student_id,
t1.num,
t2.num
from
(
select
student_id,
num
from
score
where
course_id = (
select
cid
from
course
where
cname = '物理'
)
) as t1
inner join (
select
student_id,
num
from
score
where
course_id = (
select
cid
from
course
where
cname = '生物'
)
) as t2 on t1.student_id = t2.student_id
where
t1.num > t2.num;
9、 查询没有同时选修物理课程和体育课程的学生姓名
# 包含了物理，体育都没选得
select
sname
from
student
where
sid not in (
select
t1.student_id
from
(
select
student_id,
course_id
from
score
where
course_id in (
select
cid
from
course
where
cname in (
'物理',
'体育'
)
)
) as t1
group by
t1.student_id
having
count(t1.student_id) = 2
);
# 只选修了一门
select
sname
from
student
where
sid in (
select
t1.student_id
from
(
select
student_id,
course_id
from
score
where
course_id in (
select
cid
from
course
where
cname in (
'物理',
'体育'
)
)
) as t1
group by
t1.student_id
having
count(t1.student_id) = 1
);
# 另一种方法：
SELECT
student.sname
FROM
student
WHERE
sid IN (
SELECT
student_id
FROM
score
WHERE
course_id IN (
SELECT
cid
FROM
course
WHERE
cname = '物理'
OR cname = '体育'
)
GROUP BY
student_id
HAVING
COUNT(course_id) = 1
);
10、查询挂科超过两门(包括两门)的学生姓名和班级
select
t1.caption,
t2.sname
from
class as t1
inner join (
select
sname,
class_id
from
student
where
sid in (
select
student_id
from
score
where
num < 60
group by
student_id
having
count(sid) >= 2
)
) as t2 on t1.cid = t2.class_id;
#另一种方法：
SELECT
student.sname,
class.caption
FROM
student
INNER JOIN (
SELECT
student_id
FROM
score
WHERE
num < 60
GROUP BY
student_id
HAVING
count(course_id) >= 2
) AS t1
INNER JOIN class ON student.sid = t1.student_id
AND student.class_id = class.cid;
11、查询选修了所有课程的学生姓名
select
sname
from
student
where
sid in (
select
student_id
from
score
group by
student_id
having
count(sid) = (
select
count(cid)
from
course
)
);
12、查询李平老师教的课程的所有成绩记录
select
*
from
score
where
course_id in (
select
cid
from
course
inner join teacher on course.teacher_id = teacher.tid
where
teacher.tname = '李平老师'
);
13、查询全部学生都选修了的课程号和课程名(取所有学生数，然后基于score表的课程分组，找出count(student_id)等于学生数即可)
select
cid,
cname
from
course
where
cid in (
select
course_id
from
score
group by
course_id
having
count(sid) = (select count(sid) from student)
);
14、查询每门课程被选修的次数
select
course_id,
count(sid)
from
score
right join course on score.course_id = course.cid
group by
course_id
order by
course_id;
SELECT
course_id,
COUNT(student_id)
FROM
score
GROUP BY
course_id;
15、查询之选修了一门课程的学生姓名和学号
select
sid,
sname
from
student
where
sid in (
select
student_id
from
score
group by
student_id
having
count(sid) = 1
);
16、查询所有学生考出的成绩并按从高到低排序（成绩去重）
select distinct
num
from
score
order by
num desc;
17、查询平均成绩大于85的学生姓名和平均成绩
select
student.sname,
t1.avg_num
from
student
inner join (
select
student_id,
avg(num) as avg_num
from
score
group by
student_id
having
avg(num) > 85
) as t1 on student.sid = t1.student_id;
18、查询生物成绩不及格的学生姓名和对应生物分数
select
sname,
t1.num
from
student
inner join (
select
student_id,
num
from
score
inner join course on score.course_id = course.cid
where course.cname = '生物'
and score.num < 60
) as t1 on student.sid = t1.student_id;
# 另一种方法：
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
course.cname = '生物'
and score.num < 60;
19、查询在所有选修了李平老师课程的学生中，这些课程(李平老师的课程，不是所有课程)平均成绩最高的学生姓名
select
sname,
t1.avg_num
from
student
inner join (
select
student_id,
avg(num) as avg_num
from
score
where
course_id in (
select
cid
from
course
inner join teacher on course.teacher_id = teacher.tid
where teacher.tname = '李平老师'
)
group by
student_id
order by
avg_num desc
limit 1
) as t1 on student.sid = t1.student_id;
20、查询每门课程成绩最好的前两名学生姓名
select
student.sname,
num_table.course_id,
num_table.first_num,
num_table.second_num
from
student
inner join (
select
score.sid,
score.course_id as course_id,
score.student_id,
t.first_num as first_num,
t.second_num as 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 s3 where s3.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
) as num_table on student.sid = num_table.student_id;
21、查询不同课程但成绩相同的学号，课程号，成绩
select distinct
s1.student_id,
s1.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;
select distinct
*
from
score as s1,
score as s2
where
s1.num = s2.num
22、查询没学过李平老师课程的学生姓名以及选修的课程名称；
select
student.sname,
course.cname
from
(
select
student_id,
course_id
from
score
where
course_id not in (
select
cid
from
course
inner join teacher on course.teacher_id = teacher.tid
where teacher.tname = '李平老师'
)
) as t1
inner join course on t1.course_id = course.cid
inner join student on t1.student_id = student.sid
order by student.sname;
23、查询所有选修了学号为1的同学选修过的一门或者多门课程的同学学号和姓名；
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
# 另一种方法：
select
sid,
sname
from
student
where
sid in (
select
student_id
from
score
where
course_id in (
select
course_id
from
score
where
student_id = 1
)
)
and sid !=1
24、任课最多的老师中学生单科成绩最高的学生姓名
select
sid,
sname
from
student
where
sid in (
select distinct
t1.id_students
from
(
select
group_concat(student_id) as id_students,
course_id,
max(num)
from
score
where
course_id in (
select
cid
from
course
where
teacher_id in (
select
teacher_id
from
course
group by
teacher_id
having
count(cid) = (
select
count(cid)
from
course
group by
teacher_id
order by
count(cid) desc
limit 1
)
)
)
group by
course_id
) as t1
);
