【MYSQL数据库综合练习】第一部分_mysql练习题分数段统计-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_49278249/article/details/127659255

MySQL通关练习题目

运行创建数据库

drop table if exists student;

drop table if exists teacher;

drop table if exists course;

drop table if exists sc;

create table student(

sno varchar(10) primary key,

sname varchar(20),

sage int,

ssex varchar(5)

);

create table teacher(

tno varchar(10) primary key,

tname varchar(20)

);

create table course(

cno varchar(10),

cname varchar(20),

tno varchar(20),

constraint pk_course primary key (cno,tno)

);

create table sc(

sno varchar(10),

cno varchar(10),

score decimal(8,2),

constraint pk_sc primary key (sno,cno)

);

/*初始化学生表的数据/

insert into student values (‘s001’,‘张三’,23,‘男’);

insert into student values (‘s002’,‘李四’,23,‘男’);

insert into student values (‘s003’,‘吴鹏’,25,‘男’);

insert into student values (‘s004’,‘琴沁’,20,‘女’);

insert into student values (‘s005’,‘王丽’,20,‘女’);

insert into student values (‘s006’,‘李波’,21,‘男’);

insert into student values (‘s007’,‘刘玉’,21,‘男’);

insert into student values (‘s008’,‘萧蓉’,21,‘女’);

insert into student values (‘s009’,‘陈萧晓’,23,‘女’);

insert into student values (‘s010’,‘陈美’,22,‘女’);

/初始化教师表*****/

insert into teacher values (‘t001’, ‘刘阳’);

insert into teacher values (‘t002’, ‘谌燕’);

insert into teacher values (‘t003’, ‘胡明星’);

/初始化课程表*************/

insert into course values (‘c001’,‘J2SE’,‘t002’);

insert into course values (‘c002’,‘Java Web’,‘t002’);

insert into course values (‘c003’,‘SSH’,‘t001’);

insert into course values (‘c004’,‘Oracle’,‘t001’);

insert into course values (‘c005’,‘SQL SERVER 2005’,‘t003’);

insert into course values (‘c006’,‘C#’,‘t003’);

insert into course values (‘c007’,‘JavaScript’,‘t002’);

insert into course values (‘c008’,‘DIV+CSS’,‘t001’);

insert into course values (‘c009’,‘PHP’,‘t003’);

insert into course values (‘c010’,‘EJB3.0’,‘t002’);

/初始化成绩表********/

insert into sc values (‘s001’,‘c001’,78.9);

insert into sc values (‘s002’,‘c001’,80.9);

insert into sc values (‘s003’,‘c001’,81.9);

insert into sc values (‘s004’,‘c001’,60.9);

insert into sc values (‘s001’,‘c002’,82.9);

insert into sc values (‘s002’,‘c002’,72.9);

insert into sc values (‘s003’,‘c002’,81.9);

insert into sc values (‘s001’,‘c003’,59);

insert into sc values (‘s001’,‘c004’,78.9);

insert into sc values (‘s002’,‘c004’,80.9);

insert into sc values (‘s003’,‘c005’,81.9);

insert into sc values (‘s004’,‘c005’,60.9);

insert into sc values (‘s001’,‘c006’,82.9);

insert into sc values (‘s002’,‘c006’,72.9);

insert into sc values (‘s003’,‘c007’,81.9);

insert into sc values (‘s001’,‘c007’,59);

insert into sc values (‘s005’,‘c001’,80.9);

insert into sc values (‘s006’,‘c001’,81.9);

insert into sc values (‘s007’,‘c001’,90.9);

insert into sc values (‘s004’,‘c002’,75);

insert into sc values (‘s005’,‘c002’,71.2);

insert into sc values (‘s006’,‘c002’,85.9);

insert into sc values (‘s007’,‘c003’,59);

insert into sc values (‘s004’,‘c004’,77.9);

insert into sc values (‘s005’,‘c004’,84.9);

insert into sc values (‘s006’,‘c005’,82.9);

insert into sc values (‘s007’,‘c005’,67.9);

insert into sc values (‘s004’,‘c006’,62.9);

insert into sc values (‘s006’,‘c006’,92.9);

insert into sc values (‘s007’,‘c007’,35.9);

insert into sc values (‘s008’,‘c007’,69);

练习：
注意：以下练习中的数据是根据初始化到数据库中的数据来写的SQL 语句，请大家务必注意。

1、查询“c001”课程比“c002”课程成绩高的所有学生的学号；

SELECT
  sc1.sno 
FROM sc sc1,sc sc2 
WHERE
sc1.sno = sc2.sno AND sc1.cno = 'c001' AND sc2.cno = 'c002' AND sc1.score > sc2.score

知识点：

1、子查询（查询结果作为数据表）

2、聚合函数的使用。（没有在聚合函数中的字段，必须包含在group by子句中）——分组统计。

聚合函数总共有5个（sum,count,max,min,avg）。作用：统计

3、case… when…else…end（相当与程序里面的if…else…）

(1) Case…when…when…else…end

(2) Case when…when…else…end

2、查询平均成绩大于60 分的同学的学号和平均成绩；

方法一：

SELECT sno,AVG(score) FROM sc
WHERE sno IN (SELECT sno FROM sc GROUP BY sno HAVING AVG(score)>60)
GROUP BY sno
HAVING AVG(score)

知识点：

1、子查询

2、聚合函数

3、统计结果列不能用在where条件中

方法二：

SELECT sno,AVG(score) FROM sc
GROUP BY sno
HAVING AVG(score)>60

知识点：

1、having–用来过滤统计字段

3、查询所有同学的学号、姓名、选课数、总成绩；

分析：学号，姓名在student表

选课数：统计字段–>来源（sc 表）

总成绩：统计字段（来源：SC表）

结果sql：

SELECT student.sno,student.sname,COUNT(sc.cno),SUM(sc.score) 
FROM student RIGHT JOIN sc ON sc.sno=student.sno
GROUP BY student.sno,student.sname

4、查询姓“刘”的老师的个数；

分析:字段（老师个数）—来源（teacher表）

涉及：模糊查询

SELECT COUNT(tname) FROM teacherWHERE tname LIKE '刘%'

5、查询没学过“谌燕”老师课的同学的学号、姓名；

分析：

1、查询字段（学号，姓名）–student表

2、条件：teacher表姓名=‘谌燕’–>tno->(course–>cno)–>(sc->查找没有记录的)

SELECT sno,sname 
FROM student
WHERE sno NOT IN (SELECT sno FROM scWHERE cno IN (SELECT cno FROM course INNER JOIN teacherWHERE tname='谌燕'))

6、查询学过“c001”并且也学过编号“c002”课程的同学的学号、姓名；

方法一：

分析：结果(学号，姓名–>student)

条件：–>sc表(查询出既有c001课程和c002课程的学号)—>先将有c001的学号找到，然后再找还有c002的。

SELECT sno,sname 
FROM student
WHERE sno IN (SELECT sno FROM sc WHERE cno='c001' AND sno IN (SELECT sno FROM sc WHERE cno='c002'))

知识点：in（集合）关键字。作为查询条件。例如：sno in(‘002’,’003’)–>表示，sno等于002或者003的结果。在in(集合)的集合中，我们可以使用子查询，注意：子查询的结果应该是只有一列

方法二：

分析：如果只需要查询学过c001课程的学生

SELECT sno FROM studentWHERE sno IN (SELECT sno FROM sc WHERE cno='c001')

在这个结果的基础上再去找学过c002的学生

SELECT sno,sname 
FROM student 
WHERE sno IN (SELECT sno FROM studentWHERE sno IN (SELECT sno FROM sc WHERE cno='c001')) AND sno IN (SELECT sno FROM sc WHERE cno='c002')

7、查询学过“谌燕”老师所教的所有课的同学的学号、姓名；

分析：结果（student–>学号，姓名）

条件：teacher(tname=’谌燕’)–>course(所有的cno)==》cno的集合

SELECT cno FROM course INNER JOIN teacher ON course.tno=teacher.tnoWHERE teacher.tname='谌燕'

==>分组统计（某个学生选了多少门‘谌燕’老师的课程）

SELECT COUNT(cno) 
FROM student INNER JOIN sc ON student.sno=sc.sno
WHERE cno IN (SELECT cno FROM course INNER JOIN teacher ON course.tno=teacher.tnoWHERE teacher.tname='谌燕')GROUP BY sc.sno

==>判断学生选课数量等于‘谌燕’老师所教课程的数量

SELECT student.sno,student.sname 
FROM student INNER JOIN sc ON student.sno=sc.sno
WHERE cno IN (SELECT cno FROM course INNER JOIN teacher ON course.tno=teacher.tnoWHERE teacher.tname='谌燕')
GROUP BY student.sno,student.sname
-- 用having判断学生选课数量等于‘谌燕’老师所教课程的数量
HAVING COUNT(cno)=(SELECT COUNT(cno) FROM course INNER JOIN teacher ON course.tno=teacher.tnoWHERE teacher.tname='谌燕')

*8、查询课程编号“c002”的成绩比课程编号“c001”课程低的所有同学的学号、姓名；

select student.sno,student.sname from student where student.sno in (
select sc2.sno from sc sc1 ,sc sc2 where sc1.sno=sc2.sno and sc1.cno='c001' and sc2.cno='c002' and sc2.score<sc1.score)

9、查询所有课程成绩小于60 分的同学的学号、姓名；

SELECT sno,sname FROM student

-- 逆向思维，先求有一个60分以上的学号，再用NOT IN 求解

WHERE sno NOT IN (SELECT sno FROM sc WHERE score>=60)

10、查询没有学全所有课的同学的学号、姓名；

SELECT student.sno 
FROM sc RIGHT JOIN student ON student.sno=sc.sno
GROUP BY student.sno 
HAVING COUNT(sc.cno) < (SELECT COUNT(cno) FROM course)

11、查询至少有一门课与学号为“s001”的同学所学相同的同学的学号和姓名；

select sno,sname
from student
where sno in (
select sno 
from sc
where cno in(
select cno
from sc
where sno='s008')) and sno !='s008'

12、查询至少学过学号为“s001”同学所有课的其他同学学号和姓名；

分析：

1、找到学号s001的同学所学的所有课程

2、找到学过这些课程的同学名单

SELECT DISTINCT student.sno,student.sname 
FROM student INNER JOIN sc ON student.sno=sc.sno
WHERE sc.cno IN (SELECT cno FROM sc WHERE sno='s001') AND student.sno!='s001'

知识点：in和exists的区别

1、in（）确定给定的值是否与子查询或列表中的值相匹配。in在查询的时候，首先查询子查询的表，然后将内表和外表做一个笛卡尔积，然后按照条件进行筛选。所以相对内表比较小的时候，in的速度较快。

2、exists指定一个子查询，检测行的存在。遍历循环外表，然后看外表中的记录有没有和内表的数据一样的。匹配上就将结果放入结果集中。

3、区别及使用场景：内表结果大用exists；内表结果小用In

not in 和not exists

如果查询语句使用了not in 那么内外表都进行全表扫描，没有用到索引；而not extsts 的子查询依然能用到表上的索引。所以无论那个表大，用not exists都比not in要快。

*13、把“SC”表中“谌燕”老师教的课的成绩都更改为此课程的平均成绩；

UPDATE sc SET score=(SELECT s.a FROM (SELECT avgsco.a,avgsco.cno FROM (SELECT cno,AVG(score) AS a FROM sc WHERE cno IN (SELECT cno FROM course INNER JOIN teacher ON teacher.tno=course.tno WHERE teacher.tname='谌燕')
                                                                       
-- 不对的地方：没办法将平均成绩和update里要修改的成绩对应
GROUP BY cno) AS avgsco) as s WHERE s.cno=cno) 
WHERE cno IN (SELECT cno FROM sc WHERE cno IN (SELECT cno FROM course INNER JOIN teacher ON teacher.tno=course.tno WHERE teacher.tname='谌燕'))

-- UPDATE在更新这个表和数据时又查询了它，而查询的数据又做了更新的条件,所以用别名，但是平均成绩有多行,再对这个表查询，产生一个包含平均成绩和课程号的表s
SELECT s.a FROM (SELECT avgsco.a,avgsco.cno FROM (SELECT cno,AVG(score) AS a FROM sc WHERE cno IN (SELECT cno FROM course INNER JOIN teacher ON teacher.tno=course.tno WHERE teacher.tname='谌燕')
GROUP BY cno) AS avgsco) as s WHERE s.cno=sc.cno

-- 求所教课程
SELECT cno FROM sc 
WHERE cno IN (SELECT cno FROM course INNER JOIN teacher ON teacher.tno=course.tno WHERE teacher.tname='谌燕')

-- 求所教课程的平均成绩
SELECT AVG(score) FROM sc WHERE cno IN (SELECT cno FROM course INNER JOIN teacher ON teacher.tno=course.tno WHERE teacher.tname='谌燕')
GROUP BY cno

订正

update sc s1 join (select sc,cno,avg(sc.score) avgscore form course,teacher,sc
where course.tno=teacher.tno
and course.cno=sc.cno
and teacher.tname='谌燕'
group by sc.cno) s2 ON s1.cno = s2.cno
SET s1.score=s2.avgscore

14、查询和“s001”号的同学学习的课程完全相同的其他同学学号和姓名；

-- s001同学学习的课程
SELECT cno FROM sc WHERE sno='s001'

-- c001 c002 c003 c004 c006 c007

-- 借鉴思路：逆向思维先求cno有一门和s001不一样的，就可以排除一部分，之后其他的都是要么少于s001的，要么是和s001相同的
SELECT sno FROM sc
WHERE cno NOT IN ((SELECT sc.cno FROM sc WHERE sc.sno='s001'))
GROUP BY sno

-- 此时再对sno反选，选出所选课要么少于s001的，要么是和s001相同的
SELECT sno FROM sc
WHERE sno NOT IN 
(SELECT sno FROM sc
WHERE cno NOT IN ((SELECT sc.cno FROM sc WHERE sc.sno='s001'))
GROUP BY sno
) AND sno<>'s001'
GROUP BY sno 

-- 再对比符合条件的数量
HAVING COUNT(cno)=(SELECT COUNT(cno) FROM sc WHERE sc.sno='s001')

15、删除学习“谌燕”老师课的SC 表记录；

select from sc where cno IN (
select cno from course where tno in(
select tno from teacher where tname='谌燕'))

16、向SC 表中插入一些记录，这些记录要求符合以下条件：没有上过编号“c002”课程的同学学号、“c002”号课的平均成绩；

-- “c002”号课的平均成绩
SELECT AVG(score)  FROM sc
WHERE cno='c002'

-- 没有上过编号c002课程的同学学号
SELECT DISTINCT sno FROM sc
WHERE sno NOT IN (SELECT sno FROM sc
WHERE cno='c002'
GROUP BY sno)

-- 将两个表连起来
SELECT * FROM (SELECT DISTINCT sno FROM sc
WHERE sno NOT IN (SELECT sno FROM sc
WHERE cno='c002'
GROUP BY sno)) as s2,(SELECT AVG(score)  FROM sc WHERE cno='c002') as s1

-- 添加记录
-- 参考了怎么将一个表插入到另一个表当中：(
-- 如果只希望导入指定字段，可以用这种方法：
-- INSERT INTO 目标表 (`字段1`, `字段2`, ...) SELECT `字段1`, `字段2`, ... FROM 来源表;(这里的话字段必须保持一致)
-- insert into insertTest2(`id`) select `id` from insertTest2;
-- )

INSERT INTO sc(sno,cno,score) SELECT s.sno,'c002',s.a FROM (SELECT * FROM (SELECT DISTINCT sno FROM sc
WHERE sno NOT IN (SELECT sno FROM sc
WHERE cno='c002'
GROUP BY sno)) as s2,(SELECT AVG(score) AS a FROM sc WHERE cno='c002') as s1
) AS s

17、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 cno,MAX(score),MIN(score) FROM sc
GROUP BY cno

*18、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

select cno,avg(score),(sum(case when score>60 then 1 else 0 end)/COUNT(*))*100 passline
from sc
group by cno
order by  AVG(score) asc,passline desc

19、查询不同老师所教不同课程平均分从高到低显示

SELECT teacher.tname,AVG(score) FROM sc INNER JOIN (teacher,course) 
ON sc.cno=course.cno AND teacher.tno = course.tno
GROUP BY sc.cno,teacher.tname

*20、统计列印各科成绩,各分数段人数:课程ID,课程名称,[100-85],[85-70],[70-60],[ <60]

SELECT sc.cno,course.cname ,SUM(CASE WHEN score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS '[100-85]'
,SUM(CASE WHEN score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS '[85-70]'
,SUM(CASE WHEN score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS '[70-60]'
,SUM(CASE WHEN score <60 THEN 1 ELSE 0 END) AS '[ <60]'
FROM sc INNER JOIN course ON course.cno=sc.cno
GROUP BY sc.cno,course.cname

*21、查询各科成绩前三名的记录:(不考虑成绩并列情况)

select a.cno,a.first_score, b.second_score from (select cno,max( score)(select s.cno ,max(s.score) second_score from sc s,
( select cno,max ( score) first_score from sc group by cno) awhere s.cno = a.cno
and s.score < a.first_scoregroup by s.cno) b
where a.cno = b.cno

22、查询每门课程被选修的学生数

SELECT course.cname,COUNT(sno) FROM sc INNER JOIN course ON sc.cno=course.cno
GROUP BY sc.cno,course.cname

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.sno,student.sname FROM student INNER JOIN sc ON student.sno=sc.sno
GROUP BY sno
HAVING COUNT(cno)=1

24、查询男生、女生人数

SELECT ssex,COUNT(ssex) FROM student
GROUP BY ssex
HAVING COUNT(ssex)

25、查询姓“张”的学生名单

SELECT * FROM student
WHERE sname LIKE '张%'

26、查询同名同性学生名单，并统计同名人数

SELECT *,(SELECT COUNT(s1.sno) 
FROM student AS s1 INNER JOIN student AS s2 ON s1.sname=s2.sname AND s1.ssex=s2.ssex AND s1.sno!=s2.sno) AS '同名人数' FROM student AS s1 
INNER JOIN student AS s2 ON s1.sname=s2.sname AND s1.ssex=s2.ssex AND s1.sno!=s2.sno

27、1981 年出生的学生名单(注：Student 表中Sage 列的类型是int)

select * from student where student.sage = (SELECT DATE_FORMAT(NOW(), '%Y')-1981)

28、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 AVG(score) FROM sc
GROUP BY cno
ORDER BY AVG(score) ASC,cno DESC

29、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.sno,student.sname,AVG(score) FROM student INNER JOIN sc ON student.sno=sc.sno
GROUP BY student.sno,student.sname
HAVING AVG(score)>85

30、查询课程名称为“数据库”，且分数低于60 的学生姓名和分数

SELECT sname,score FROM student INNER JOIN (sc,course) ON student.sno=sc.sno AND course.cno=sc.cno

WHERE (cname='Oracle' OR cname='SQL SERVER 2005') AND score<60

31、查询所有学生的选课情况；

SELECT student.*,sc.cno FROM student LEFT JOIN sc on student.sno=sc.sno

32、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 student.sname,course.cname,sc.score FROM student INNER JOIN (course,sc) 
ON student.sno=sc.sno AND course.cno=sc.cno
WHERE score>70

33、查询不及格的课程，并按课程号从大到小排列

SELECT course.cname,course.cno,sc.score,sc.sno FROM course INNER JOIN sc ON course.cno=sc.cno
WHERE sc.score<60
ORDER BY course.cno DESC

34、查询课程编号为c001 且课程成绩在80 分以上的学生的学号和姓名；

SELECT student.sno,student.sname,sc.score FROM student INNER JOIN sc ON student.sno=sc.sno
WHERE cno='c001' AND score>=80

35、求选了课程的学生人数

SELECT COUNT(DISTINCT sno) FROM sc

36、查询选修“谌燕”老师所授课程的学生中，成绩最高的学生姓名及其成绩

SELECT student.sname,sc.score FROM sc INNER JOIN student ON student.sno=sc.sno
WHERE sc.cno IN (SELECT course.cno FROM teacher INNER JOIN course ON teacher.tno=course.tno
WHERE tname='谌燕')
ORDER BY score DESC
LIMIT 1

37、查询各个课程及相应的选修人数

SELECT course.cno,course.cname,COUNT(sno) FROM course INNER JOIN sc ON sc.cno=course.cno
GROUP BY course.cno,course.cname
HAVING COUNT(sno)

*38、查询不同课程成绩相同的学生的学号、课程号、学生成绩

SELECT s1.sno,s1.cno,s1.score FROM sc AS s1 INNER JOIN sc AS s2 ON s1.sno=s2.sno
WHERE s1.score =s2.score AND s1.cno!=s2.cno

*39、查询每门功课成绩最好的前两名

select s1.* from sc s1 where (select count(1) from sc s2 where s1.cno=s2.cno  and s2.score>=s1.score) <=2 ORDER BY s1.score desc;

40、统计每门课程的学生选修人数（超过10 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 cno,COUNT(sno) FROM sc
GROUP BY cno
HAVING COUNT(sno)>10
ORDER BY COUNT(sno) DESC,cno ASC

41、检索至少选修两门课程的学生学号

SELECT sno FROM sc
GROUP BY sno
HAVING COUNT(cno)>=2

*42、查询全部学生都选修的课程的课程号和课程名

SELECT course.cno,course.cname FROM student INNER JOIN (course,sc) ON student.sno=sc.sno AND sc.cno=course.cno
GROUP BY course.cno,course.cname
HAVING COUNT(*)=(SELECT COUNT(*) FROM student)

43、查询没学过“谌燕”老师讲授的任一门课程的学生姓名

SELECT DISTINCTsname FROM student INNER JOIN sc
WHERE sc.cno NOT IN (SELECT cno FROM course INNER JOIN teacher ON teacher.tno=course.tno
WHERE tname='谌燕')

*44、查询两门以上不及格课程的同学的学号及其平均成绩

select sno ,avg(sc.score)  from sc  GROUP BY sno having count(case when sc.score<60 then 1 else null end)>=2

*45、检索“c004”课程分数小于60，按分数降序排列的同学学号

select * from sc where sc.cno='c004' and sc.score<60 ORDER BY sc.score asc;

*46、删除“s002”同学的“c001”课程的成绩

delete from sc where sc.sno='s002' and sc.cno='c001'