MySQL练习题

　　一、表关系

　　二、操作表

1、自行创建测试数据；

/*
 Navicat Premium Data Transfer

 Source Server         : localhost
 Source Server Type    : MySQL
 Source Server Version : 50624
 Source Host           : localhost
 Source Database       : sqlexam

 Target Server Type    : MySQL
 Target Server Version : 50624
 File Encoding         : utf-8

 Date: 10/21/2016 06:46:46 AM
*/

SET NAMES utf8;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
--  Table structure for `class`
-- ----------------------------
DROP TABLE IF EXISTS `class`;
CREATE TABLE `class` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `caption` varchar(32) NOT NULL,
  PRIMARY KEY (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `class`
-- ----------------------------
BEGIN;
INSERT INTO `class` VALUES ('1', '三年二班'), ('2', '三年三班'), ('3', '一年二班'), ('4', '二年九班');
COMMIT;

-- ----------------------------
--  Table structure for `course`
-- ----------------------------
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`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `course`
-- ----------------------------
BEGIN;
INSERT INTO `course` VALUES ('1', '生物', '1'), ('2', '物理', '2'), ('3', '体育', '3'), ('4', '美术', '2');
COMMIT;

-- ----------------------------
--  Table structure for `score`
-- ----------------------------
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`)
) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `score`
-- ----------------------------
BEGIN;
INSERT INTO `score` 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');
COMMIT;

-- ----------------------------
--  Table structure for `student`
-- ----------------------------
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`)
) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `student`
-- ----------------------------
BEGIN;
INSERT INTO `student` 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');
COMMIT;

-- ----------------------------
--  Table structure for `teacher`
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
  `tid` int(11) NOT NULL AUTO_INCREMENT,
  `tname` varchar(32) NOT NULL,
  PRIMARY KEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `teacher`
-- ----------------------------
BEGIN;
INSERT INTO `teacher` 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');
COMMIT;

SET FOREIGN_KEY_CHECKS = 1;

2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；

select A.student_id from 
(select num,student_id from score left join course on course.cid=score.course_id 
where course.cname='生物')as A
inner join
(select num,student_id from score left join course on course.cid=score.course_id 
where course.cname='物理')as B
on A.student_id=B.student_id
where A.num>B.num

　　

3、查询平均成绩大于60分的同学的学号、姓名和平均成绩；

select student_id,student.sname,avg(num) from score 
left join student on student.sid=score.student_id 
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 student_id as 学号,student.sname as 姓名,count(1)as 选课数,sum(if(isnull(num),0,num))as 总成绩 from score 
left join student on student.sid=score.student_id group by student_id

　　

5、查询姓“李”的老师的个数；

select count(1) from teacher where tname like '李%'

　　

6、查询没学过“李平”老师课的同学的学号、姓名；

select student.sid,student.sname from student
where student.sid not in 
(
select student_id from score where course_id in
(select cid from course left join teacher on teacher.tid=course.teacher_id
where teacher.tname='李平老师')
)

　　

7、查询学过“001”并且也学过编号“003”课程的同学的学号、姓名；

方法一：
select student_id,student.sname from score left join student on student.sid=score.student_id
where student_id in 
(select student_id from score where course_id=1)
and 
student_id in 
(select student_id from score where course_id=3)
group by student_id

方法二：
SELECT student_id,student.sname FROM
	(SELECT score.student_id FROM score WHERE course_id = 1 OR course_id = 3) AS A
LEFT JOIN student ON A.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；

select student_id,student.sname from score left join student on student.sid=score.student_id
where course_id in
(
select cid from course left join teacher on teacher.tid=course.teacher_id 
where teacher.tname='李平老师'
) group by student_id having count(1)=(select count(1) from course left join teacher on teacher.tid=course.teacher_id 
where teacher.tname='李平老师')

　　

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；

方法一：
select student_id,student.sname from score left join student on student.sid=score.student_id
where student_id in
(
select A.student_id from
(select num,student_id from score where course_id=2) as A
inner join 
(select num,student_id from score where course_id=1)as B
on A.student_id=B.student_id
where A.num<B.num
)group by student_id

方法二：
select student.sid,student.sname from
(
	select A.student_id from
		(select score.student_id,score.num from score where course_id = 2)as A
		inner join 
		(select score.student_id,score.num from score where course_id = 1)as B 
		on A.student_id = B.student_id
		where A.num < B.num
)as C
	left join student on C.student_id = student.sid

　　

10、查询有课程成绩小于60分的同学的学号、姓名；

select student_id,student.sname from score left join student on 
score.student_id=student.sid where num<60 GROUP BY student_id

　　

11、查询没有学全所有课的同学的学号、姓名；

方法一：
select student_id,student.sname from score left join student on student.sid=score.student_id
where student_id in 
(
select student_id from score where course_id in
(select cid from course)
)group by student_id having count(1)<(select count(1) from course)

方法二：
select student.sid,student.sname from
(select score.student_id from score where score.course_id in 
(select course.cid from course ) GROUP BY score.student_id HAVING count(score.student_id)<4
)as A
LEFT JOIN student on student.sid= A.student_id

　　

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；

方法一：
select student_id,student.sname from score left join student on student.sid=score.student_id
where student_id in 
(
select student_id from score where course_id in 
(select course_id from score where student_id=1)
)and student_id!=1
group by student_id

方法二：
select student.sid,student.sname from 
(select student_id from score where 
student_id in
(select student_id from score where course_id=1)and student_id!=1
 GROUP BY student_id
)as A
LEFT JOIN student on student.sid=A.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；

方法一：
select student_id,student.sname from score left join student on student.sid=score.student_id 
where student_id in 
(
select student_id from score where course_id in
(select course_id from score where student_id=1)
and student_id!=1)group by student_id

方法二：
select student.sid,student.sname from 
(select student_id from score where course_id in
(select course_id from score where student_id=1)and student_id!=1
)as A
LEFT JOIN student on student.sid=A.student_id GROUP BY student_id

　　

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；

select student_id,student.sname from score left join student on student.sid=score.student_id 
where student_id in
(
select student_id from score where course_id in
(select course_id from score where student_id=2 ) group by student_id 
having count(student_id)>=(select count(1) from score where student_id=2)
and student_id!=2
)group by student_id

　　

15、删除学习“李平”老师课的score表记录；

delete from score where course_id in
(
select cid from course left join teacher on teacher.tid=course.teacher_id
where teacher.tname='李平老师'
)

　　

16、向score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； 

insert into score(student_id,course_id,num)
select student_id,3,(select avg(num) from score where course_id=2) from score where course_id !=2 group by student_id

　　

17、按平均成绩从低到高显示所有学生的“生物”、“物理”、“美术”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 
	s1.student_id,
	(select num from score left join course on course.cid=score.course_id where course.cname='生物' and score.student_id=s1.student_id)as 生物,
	(select num from score left join course on course.cid=score.course_id where course.cname='物理' and score.student_id=s1.student_id)as 物理,
	(select num from score left join course on course.cid=score.course_id where course.cname='美术' and score.student_id=s1.student_id)as 美术,
	count(course_id)as 有效课程数,
	avg(if(isnull(s1.num),0,s1.num))as 平均分
from score as s1 
group by s1.student_id order by 平均分 asc

　　

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),min(num) from score group by course_id

    知识点：1、case when 条件 then 条件成立时... else 不成立时... end

	   2、if(isnull(num),0,num) 判断num是否为空，为空赋值为0，不为空则是num本身的值

　　

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；

select avg(if(isnull(num),0,num))as avg,sum(case when num<60 then 0 else 1 end)/count(1)*100 as 及格率 
from score group by course_id order by avg asc,及格率 desc

　　

20、课程平均分从高到低显示（现实任课老师）；

select course.cname,teacher.tname,avg(if(isnull(num),0,num)) from score left join course on course.cid=score.course_id 
left join teacher on teacher.tid=course.teacher_id group by score.course_id order by avg(num) desc

　　

21、查询各科成绩前三名的记录:(不考虑成绩并列情况) ;

select * from 
(
select 
student_id,
course_id,
num,
(select num from score as s2 where s2.course_id=s1.course_id group by s2.num order by s2.num desc limit 0,1) as first_num,
(select num from score as s2 where s2.course_id=s1.course_id group by s2.num order by s2.num desc limit 1,1) as second_num,
(select num from score as s2 where s2.course_id=s1.course_id group by s2.num order by s2.num desc limit 2,1)as third_num

from score as s1
)as A
where A.num>=A.third_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_id,student.sname from score left join student on student.sid=score.student_id 
group by student_id having count(1)=1

　　

24、查询男生、女生的人数；

select gender,count(1) from student group by gender

　　

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) from student group by sname having count(1)>1

　　

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 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,student.sname,avg(num) from score left join student 
on student.sid=score.student_id group by student_id having avg(num)>85

　　

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,num from score left join course on course.cid=score.course_id 
left join student on student.sid=score.student_id
where course.cname='生物' and num < 60 

　　

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 student_id,student.sname from score left join student on score.student_id=student.sid where course_id=3 and num >80

　　

31、求选了课程的学生人数 ;

方法一：
select count(1) from (select student_id from score group by student_id)as A
方法二：
select count(distinct student_id) from score

　　

32、查询选修“刘海燕”老师所授课程的学生中，成绩最高的学生姓名及其成绩；

select sname,num from score left join student on score.student_id=student.sid where course_id in
(
select cid from course left join teacher on teacher.tid=course.teacher_id 
where teacher.tname='刘海燕老师'
) order by num desc limit 0,1

　　

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 course.cid=score.course_id 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 
	student_id,
	course_id,
	num
from score as s1 
where student_id in
(select student_id from score as s2 where s2.sid!=s1.sid and s2.course_id!=s1.course_id and s2.num = s1.num
) 

　　

35、查询每门课程成绩最好的前两名；

select course.cname,A.first_num,A.second_num from
(
select
        student_id,
	course_id,
	num,
	(select num from score where score.course_id=s1.course_id group by score.num order by num desc limit 0,1)as first_num,
	(select num from score where score.course_id=s1.course_id group by score.num order by num desc limit 1,1)as second_num
-- 	(select student from score where score.num >= ())
from score as s1 
)as A 
left join student on A.student_id=student.sid 
left join course on A.course_id=course.cid
where num<=A.first_num and num>=A.second_num group by A.course_id

　　

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(1)>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,course.cname from score left join course on score.course_id=course.cid where score.student_id in
(
select student_id from score group by student_id having count(1)=(select count(1) from course)
)
group by course_id

　　

38、查询没学过“李平”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 student_id not in
(
select student_id from score where course_id in (select cid from course left join teacher on course.teacher_id=teacher.tid where teacher.tname='李平老师')
)
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 
score.student_id as 学号,
(select avg(num) from score where student_id in (select student_id from score where num<60 GROUP BY student_id having count(1)>1))as 平均分
from score where score.student_id in (select student_id from score where num<60 GROUP BY student_id having count(1)>1) group by score.student_id 

　　

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 course_id=4 and num<60 order by num desc

41、删除“002”同学的“001”课程的成绩；

delete from score where student_id=2 and course_id=1