mysql练习

一、表关系

请创建如下表，并创建相关约束

二、操作表

1、自行创建测试数据

2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；

3、查询平均成绩大于60分的同学的学号和平均成绩； 

4、查询所有同学的学号、姓名、选课数、总成绩；

5、查询姓“李”的老师的个数；

6、查询没学过“叶平”老师课的同学的学号、姓名；

7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；

8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；

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；

10、查询有课程成绩小于60分的同学的学号、姓名；

11、查询没有学全所有课的同学的学号、姓名；

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；

13、查询至少学过学号为“001”同学所选课程中任意一门课的其他同学学号和姓名；

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；

15、删除学习“叶平”老师课的SC表记录；

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； 

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；

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；

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；

20、课程平均分从高到低显示（现实任课老师）；

21、查询各科成绩前三名的记录:(不考虑成绩并列情况) 

22、查询每门课程被选修的学生数；

23、查询出只选修了一门课程的全部学生的学号和姓名；

24、查询男生、女生的人数；

25、查询姓“张”的学生名单；

26、查询同名同姓学生名单，并统计同名人数；

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；

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；

29、查询课程名称为“数学”，且分数低于60的学生姓名和分数；

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； 

31、求选了课程的学生人数

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；

33、查询各个课程及相应的选修人数；

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；

35、查询每门课程成绩最好的前两名；

36、检索至少选修两门课程的学生学号；

37、查询全部学生都选修的课程的课程号和课程名；

38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；

39、查询两门以上不及格课程的同学的学号及其平均成绩；

40、检索“004”课程分数小于60，按分数降序排列的同学学号；

41、删除“002”同学的“001”课程的成绩；

 

参考答案：

/*
 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 aid,a.num,b.num from
-- (SELECT score.student_id as aid,score.num as num,course.cname from score
-- LEFT JOIN course on score.course_id = course.cid
-- where course.cname = '生物')as A
-- LEFT JOIN 
-- (SELECT score.student_id as bid,score.num as num ,course.cname from score
-- LEFT JOIN course on score.course_id = course.cid
-- where course.cname = '物理')as B 
-- on A.aid = b.bid
-- where a.num > b.num


-- 3、查询平均成绩大于60分的同学的学号和平均成绩； 
-- 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 student.sid,student.sname,count(student_id) as quantity,sum(num) FROM score
-- LEFT JOIN student on score.student_id = student.sid
-- GROUP BY student_id


-- 5、查询姓“李”的老师的个数；
-- SELECT COUNT(tname) from teacher where tname LIKE '李%'


-- 6、 查询没学过“叶平”老师课的同学的学号、姓名；
-- 错误的
-- SELECT student.sid,student.sname from student 
-- LEFT JOIN (SELECT * from score
-- where course_id not in (
-- SELECT cid from course
-- LEFT JOIN teacher on teacher.tid = course.teacher_id
-- WHERE teacher.tname = '李平老师' )) as b on student.sid = b.student_id
-- 正确的
-- SELECT * from student WHERE sid not in (  --not in 查询没有学过李平老师的学生id
-- SELECT student_id from score  --in 查询学过李平老师课程的学生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' ))


-- 7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
-- SELECT student_id,sname FROM student
-- LEFT JOIN
-- (select student_id,course_id from score WHERE course_id = 1 and course_id = 2) as B
-- on student.sid = b.student_id
-- 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,sname FROM student
-- LEFT JOIN
-- (select student_id,course_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'
-- )) as B
-- on student.sid = b.student_id
-- GROUP BY student_id HAVING count(student_id) > 1


-- 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；
-- select aid,a.num,b.num from
-- (SELECT score.student_id as aid,score.num as num,course.cname from score
-- LEFT JOIN course on score.course_id = course.cid
-- where course.cid = 1)as A
-- LEFT JOIN 
-- (SELECT score.student_id as bid,score.num as num ,course.cname from score
-- LEFT JOIN course on score.course_id = course.cid
-- where course.cid = 2)as B 
-- on A.aid = b.bid
-- where a.num > b.num

-- 10、查询有课程成绩小于60分的同学的学号、姓名；
-- SELECT student.sid,student.sname from student where sid in (
-- SELECT 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；
-- SELECT student_id,count(student_id),student.sname from score
-- LEFT JOIN student on score.student_id = student.sid
-- GROUP BY student_id
-- HAVING count(student_id) = (SELECT COUNT(cid) 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；
-- SELECT student.sid,student.sname 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”同学所选课程中任意一门课的其他同学学号和姓名；
-- SELECT student.sid,student.sname,count(student_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(student_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；
-- select * from score 
-- where course_id in (select course_id from score where student_id = 2)


-- 15、删除学习“叶平”老师课的SC表记录；
-- DELETE from score where course_id in
-- (SELECT teacher_id from teacher LEFT JOIN course on teacher.tid = course.teacher_id
-- where teacher.tname = '李平老师' GROUP BY teacher_id


-- 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；
-- 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“生物”、“物理”、“体育”三门的课程成绩，
-- 按如下形式显示： 学生ID,生物,物理,体育,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 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 score.course_id,max(num),min(num) from score
-- LEFT JOIN course on score.course_id = course.cid 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；
-- select course_id, avg(num) as avgnum,
-- sum(case when score.num > 60 then 1 else 0 END)/count(1)*100 as percent 
-- case when...then筛选分数大于60，大于60计作1，小于计作0
-- 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)) as avgnum,teacher.tname from score
-- -- avg(if(isnull(score.num),0,score.num))  如果列表为空计作0，否则不变
-- LEFT JOIN course on score.course_id = course.cid
-- LEFT JOIN teacher on teacher.tid = course.teacher_id
-- GROUP BY course.cname
-- ORDER BY avgnum desc


-- 21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
-- SELECT course.cname,max(num) from score
-- LEFT JOIN course on score.course_id = course.cid
-- GROUP BY course.cname
-- --正确解法
-- 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 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 * 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 course_id,avg(if(ISNULL(num),0,num)) as avg_num from score 
-- GROUP BY course_id ORDER BY avg_num 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.sid,student.sname,avg(if(ISNULL(num),0,num)) as avg_num from score
-- LEFT JOIN student on score.student_id = student.sid
-- GROUP BY student_id HAVING avg_num > 85

-- 29、查询课程名称为“生物”，且分数低于60的学生姓名和分数；
-- SELECT student.sname,score.num from score
-- LEFT JOIN student on score.student_id = student.sid
-- WHERE course_id in (
-- SELECT cid from course WHERE 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.sid,student.sname from score 
-- LEFT JOIN student on score.student_id = student.sid
-- WHERE score.course_id = 3 and num > 80

-- 31、求选了课程的学生人数
-- SELECT COUNT(1) from (SELECT count(1) from score group by student_id) as b


-- 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 student.sname,course.cname,max(num) from score
-- LEFT JOIN student on score.student_id = student.sid
-- LEFT JOIN course on score.course_id = course.cid
-- WHERE score.course_id in (
-- SELECT course.cid from teacher
-- LEFT JOIN course on teacher.tid = course.teacher_id
-- WHERE tname = '李平老师')
-- GROUP BY course_id


-- 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；
-- 两张表相乘
-- 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 course.cname,max(num) from score
-- LEFT JOIN course on score.course_id = course.cid
-- GROUP BY course.cname
-- 正确解法
--  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,count(1) from score GROUP BY student_id HAVING count(1) >= 2


-- 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 = '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 A.student_id,avg(A.num) FROM 
-- (SELECT student_id as student_id,num as num from score  WHERE num < 60) as A
-- GROUP BY A.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 * 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