MySQL练习题参考答案
导出现有数据库数据：
- mysqldump -u用户名 -p密码 数据库名称 >导出文件路径 # 结构+数据
- mysqldump -u用户名 -p密码 -d 数据库名称 >导出文件路径 # 结构
导入现有数据库数据：
- mysqldump -uroot -p密码 数据库名称 < 文件路径
/*
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;
表结构和数据
2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
select A.student_id from (select student_id,num from score LEFT JOIN course on score.course_id=course.cid WHERE course.cname="生物") as A INNER JOIN (select student_id,num from score LEFT JOIN course on score.course_id=course.cid 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、名字和平均成绩；
select student.sid,student.sname,B.numname from (select student_id,avg(num) as numname from score GROUP BY student_id HAVING AVG(num)>60) as B LEFT JOIN student on B.student_id=student.sid
4、查询所有同学的学号、姓名、选课数、总成绩；
SELECT student_id,student.sname,COUNT(course_id),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 * 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 score.course_id in (select course.cid from course LEFT JOIN teacher on course.teacher_id=teacher.tid WHERE teacher.tname="李平老师") GROUP BY student_id)
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 C.student_id,student.sname from (SELECT A.student_id from (SELECT student_id from score WHERE course_id=1) as A INNER JOIN (SELECT student_id from score WHERE course_id=2) as B on A.student_id=B.student_id) as C LEFT JOIN student on C.student_id=student.sid
8、查询学过“李平”老师所教的所有课的同学的学号、姓名；
SELECT A.student_id,student.sname from (select student_id from score WHERE score.course_id in (SELECT cid from course LEFT JOIN teacher on course.teacher_id=teacher.tid WHERE tname LIKE "李平老师") GROUP BY student_id HAVING COUNT(student_id)=(SELECT COUNT(cid) from course LEFT JOIN teacher on course.teacher_id=teacher.tid WHERE tname LIKE "李平老师") ) as A LEFT JOIN student on A.student_id=student.sid
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 student.sid,student.sname from (select A.student_id from (select student_id,num from score WHERE score.course_id=1 ) as A INNER JOIN (select student_id,num from score WHERE score.course_id=2 ) as B on A.student_id=B.student_id WHERE B.num < A.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.sid,student.sname from (select student_id from score where num < 60 GROUP BY student_id) as A LEFT JOIN student on A.student_id=student.sid
11、查询没有学全所有课的同学的学号、姓名；
select student.sid,student.sname from (select score.student_id,COUNT(student_id) from score WHERE score.course_id in (select course.cid from course) GROUP BY score.student_id HAVING COUNT(student_id)<4) as A LEFT JOIN student on A.student_id=student.sid
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 (select student_id,COUNT(student_id) from score WHERE course_id in (SELECT course_id from score WHERE student_id=1) GROUP BY student_id) as A LEFT JOIN student on A.student_id=student.sid WHERE student.sid!=1
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 from (SELECT student_id from score WHERE score.course_id in (SELECT course_id from score WHERE student_id=1) GROUP BY student_id) as A LEFT JOIN student on A.student_id=student.sid WHERE student.sid!=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 student.sid,student.sname from (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)=3) as A LEFT JOIN student on A.student_id=student.sid WHERE A.student_id!=1
15、删除学习“李平”老师课的SC表记录；
DELETE from score WHERE course_id in (SELECT course.cid from course LEFT JOIN teacher on course.teacher_id=teacher.tid WHERE teacher.tname LIKE "李平老师")
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 student_id,2,(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”、“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 student_id, (SELECT num from score as s2 WHERE s2.student_id=s1.student_id and course_id=1) as 生物, (SELECT num from score as s2 WHERE s2.student_id=s1.student_id and course_id=2) as 物理, (SELECT num from score as s2 WHERE s2.student_id=s1.student_id and course_id=3) as 体育 from score as s1
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.cid,MAX(num),MIN(num) from course LEFT JOIN score on course.cid=score.course_id 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 A.course_id,course.cname,A.numm,A.percent from (select course_id,avg(num) as numm,SUM(case when num<60 then 0 else 1 END)/COUNT(1)*100 as percent from score GROUP BY course_id ORDER BY avg(num) ASC,percent DESC) as A LEFT JOIN course on A.course_id=course.cid
20、课程平均分从高到低显示（现实任课老师）；
SELECT course_id,AVG(if(ISNULL(num),0,score.num)),course.cname,teacher.tname from score LEFT JOIN course on score.course_id=course.cid LEFT JOIN teacher on course.teacher_id=teacher.tid GROUP BY 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 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 GROUP BY num 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(student_id) 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 score.student_id=student.sid GROUP BY student_id HAVING COUNT(student_id)=1
24、查询男生、女生的人数；
SELECT * from (SELECT COUNT(1) as man from student WHERE gender="男") as A, (SELECT COUNT(1) as feman from student WHERE gender="女") as B
25、查询姓“张”的学生名单；
SELECT * from student WHERE student.sname like "张%"
26、查询同名同姓学生名单，并统计同名人数；
SELECT COUNT(1) from student GROUP BY student.sname
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 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 score.student_id,student.sname,avg(if(ISNULL(num),0,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“数学”，且分数低于60的学生姓名和分数；
第一种： SELECT student.sname,score.num from score LEFT JOIN student on score.student_id=student.sid WHERE score.course_id=(SELECT cid from course WHERE course.cname LIKE "生物") and num<60 第二种 SELECT student.sname,score.num from score LEFT JOIN student on score.student_id=student.sid LEFT JOIN course on score.course_id=course.cid 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 score.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
第一种 SELECT COUNT(1) from (SELECT student_id from score GROUP BY student_id) as A 第二种 SELECT COUNT(DISTINCT student_id) from score
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_id,student.sname,score.num from course LEFT JOIN teacher on course.teacher_id=teacher.tid LEFT JOIN score ON course.cid=score.course_id LEFT JOIN student ON score.student_id=student.sid WHERE teacher.tname="李平老师" ORDER BY score.num DESC LIMIT 1; (SELECT course_id,MAX(num) as max from score LEFT JOIN student on score.student_id=student.sid WHERE score.course_id in SELECT course.cid from course LEFT JOIN teacher on course.teacher_id=teacher.tid WHERE teacher.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_id,course.cname,COUNT(student_id) 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；
SELECT s1.student_id,s1.course_id,s1.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 score.sid,score.course_id,T.first_num,T.second_num,score.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 from score GROUP BY student_id HAVING COUNT(student_id)>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 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.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 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 student_id,AVG(num) from score WHERE num < 60 GROUP BY 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 < 90 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
