MySQL练习（一）参考答案

/* 2 Navicat Premium Data Transfer 3 4 Source Server : localhost 5 Source Server Type : MySQL 6 Source Server Version : 50624 7 Source Host : localhost 8 Source Database : sqlexam 9 10 Target Server Type : MySQL 11 Target Server Version : 50624 12 File Encoding : utf-8 13 14 Date: 10/21/2016 06:46:46 AM 15 */ 16 17 SET NAMES utf8; 18 SET FOREIGN_KEY_CHECKS = 0; 19 20 -- ---------------------------- 21 -- Table structure for `class` 22 -- ---------------------------- 23 DROP TABLE IF EXISTS `class`; 24 CREATE TABLE `class` ( 25 `cid` int(11) NOT NULL AUTO_INCREMENT, 26 `caption` varchar(32) NOT NULL, 27 PRIMARY KEY (`cid`) 28 ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; 29 30 -- ---------------------------- 31 -- Records of `class` 32 -- ---------------------------- 33 BEGIN; 34 INSERT INTO `class` VALUES (‘1‘, ‘三年二班‘), (‘2‘, ‘三年三班‘), (‘3‘, ‘一年二班‘), (‘4‘, ‘二年九班‘); 35 COMMIT; 36 37 -- ---------------------------- 38 -- Table structure for `course` 39 -- ---------------------------- 40 DROP TABLE IF EXISTS `course`; 41 CREATE TABLE `course` ( 42 `cid` int(11) NOT NULL AUTO_INCREMENT, 43 `cname` varchar(32) NOT NULL, 44 `teacher_id` int(11) NOT NULL, 45 PRIMARY KEY (`cid`), 46 KEY `fk_course_teacher` (`teacher_id`), 47 CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`) 48 ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; 49 50 -- ---------------------------- 51 -- Records of `course` 52 -- ---------------------------- 53 BEGIN; 54 INSERT INTO `course` VALUES (‘1‘, ‘生物‘, ‘1‘), (‘2‘, ‘物理‘, ‘2‘), (‘3‘, ‘体育‘, ‘3‘), (‘4‘, ‘美术‘, ‘2‘); 55 COMMIT; 56 57 -- ---------------------------- 58 -- Table structure for `score` 59 -- ---------------------------- 60 DROP TABLE IF EXISTS `score`; 61 CREATE TABLE `score` ( 62 `sid` int(11) NOT NULL AUTO_INCREMENT, 63 `student_id` int(11) NOT NULL, 64 `course_id` int(11) NOT NULL, 65 `num` int(11) NOT NULL, 66 PRIMARY KEY (`sid`), 67 KEY `fk_score_student` (`student_id`), 68 KEY `fk_score_course` (`course_id`), 69 CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`), 70 CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`) 71 ) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8; 72 73 -- ---------------------------- 74 -- Records of `score` 75 -- ---------------------------- 76 BEGIN; 77 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‘); 78 COMMIT; 79 80 -- ---------------------------- 81 -- Table structure for `student` 82 -- ---------------------------- 83 DROP TABLE IF EXISTS `student`; 84 CREATE TABLE `student` ( 85 `sid` int(11) NOT NULL AUTO_INCREMENT, 86 `gender` char(1) NOT NULL, 87 `class_id` int(11) NOT NULL, 88 `sname` varchar(32) NOT NULL, 89 PRIMARY KEY (`sid`), 90 KEY `fk_class` (`class_id`), 91 CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`) 92 ) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8; 93 94 -- ---------------------------- 95 -- Records of `student` 96 -- ---------------------------- 97 BEGIN; 98 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‘); 99 COMMIT; 100 101 -- ---------------------------- 102 -- Table structure for `teacher` 103 -- ---------------------------- 104 DROP TABLE IF EXISTS `teacher`; 105 CREATE TABLE `teacher` ( 106 `tid` int(11) NOT NULL AUTO_INCREMENT, 107 `tname` varchar(32) NOT NULL, 108 PRIMARY KEY (`tid`) 109 ) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; 110 111 -- ---------------------------- 112 -- Records of `teacher` 113 -- ---------------------------- 114 BEGIN; 115 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‘); 116 COMMIT; 117 118 SET FOREIGN_KEY_CHECKS = 1; 表结构和数据

  1 2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
  2 思路：
  3     获取所有有生物课程的人（学号，成绩） - 临时表
  4     获取所有有物理课程的人（学号，成绩） - 临时表
  5     根据【学号】连接两个临时表：
  6         学号  物理成绩   生物成绩
  7  
  8     然后再进行筛选
  9  
 10         select A.student_id,sw,ty from
 11  
 12         (select student_id,num as sw from score left join course on score.course_id = course.cid where course.cname = ‘生物‘) as A
 13  
 14         left join
 15  
 16         (select student_id,num  as ty from score left join course on score.course_id = course.cid where course.cname = ‘体育‘) as B
 17  
 18         on A.student_id = B.student_id where sw > if(isnull(ty),0,ty);
 19  
 20 3、查询平均成绩大于60分的同学的学号和平均成绩；
 21     思路：
 22         根据学生分组，使用avg获取平均值，通过having对avg进行筛选
 23  
 24         select student_id,avg(num) from score group by student_id having avg(num) > 60
 25  
 26 4、查询所有同学的学号、姓名、选课数、总成绩；
 27  
 28     select score.student_id,sum(score.num),count(score.student_id),student.sname
 29     from
 30         score left join student on score.student_id = student.sid  
 31     group by score.student_id
 32  
 33 5、查询姓“李”的老师的个数；
 34     select count(tid) from teacher where tname like ‘李%‘
 35  
 36     select count(1) from (select tid from teacher where tname like ‘李%‘) as B
 37  
 38 6、查询没学过“叶平”老师课的同学的学号、姓名；
 39     思路：
 40         先查到“李平老师”老师教的所有课ID
 41         获取选过课的所有学生ID
 42         学生表中筛选
 43     select * from student where sid not in (
 44         select DISTINCT student_id from score where score.course_id in (
 45             select cid from course left join teacher on course.teacher_id = teacher.tid where tname = ‘李平老师‘
 46         )
 47     )
 48  
 49 7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
 50     思路：
 51         先查到既选择001又选择002课程的所有同学
 52         根据学生进行分组，如果学生数量等于2表示，两门均已选择
 53  
 54     select student_id,sname from
 55  
 56     (select student_id,course_id from score where course_id = 1 or course_id = 2) as B
 57       
 58     left join student on B.student_id = student.sid group by student_id HAVING count(student_id) > 1
 59  
 60  
 61 8、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
 62  
 63     同上，只不过将001和002变成 in (叶平老师的所有课)
 64  
 65 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；
 66     同第1题
 67  
 68  
 69 10、查询有课程成绩小于60分的同学的学号、姓名；
 70          
 71     select sid,sname from student where sid in (
 72         select distinct student_id from score where num < 60
 73     )
 74  
 75 11、查询没有学全所有课的同学的学号、姓名；
 76     思路：
 77         在分数表中根据学生进行分组，获取每一个学生选课数量
 78         如果数量 == 总课程数量，表示已经选择了所有课程
 79  
 80         select student_id,sname
 81         from score left join student on score.student_id = student.sid
 82         group by student_id HAVING count(course_id) = (select count(1) from course)
 83  
 84  
 85 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；
 86     思路：
 87         获取 001 同学选择的所有课程
 88         获取课程在其中的所有人以及所有课程
 89         根据学生筛选，获取所有学生信息
 90         再与学生表连接，获取姓名
 91  
 92         select student_id,sname, count(course_id)
 93         from score left join student on score.student_id = student.sid
 94         where student_id != 1 and course_id in (select course_id from score where student_id = 1) group by student_id
 95  
 96 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；
 97         先找到和001的学过的所有人
 98         然后个数 ＝ 001所有学科     ＝＝》 其他人可能选择的更多
 99  
100         select student_id,sname, count(course_id)
101         from score left join student on score.student_id = student.sid
102         where student_id != 1 and course_id in (select course_id from score where student_id = 1) group by student_id having count(course_id) ＝ (select count(course_id) from score where student_id = 1)
103  
104 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；
105          
106         个数相同
107         002学过的也学过
108  
109         select student_id,sname from score left join student on score.student_id = student.sid where student_id in (
110             select student_id from score  where student_id != 1 group by student_id HAVING count(course_id) = (select count(1) from score where student_id = 1)
111         ) and course_id in (select course_id from score where student_id = 1) group by student_id HAVING count(course_id) = (select count(1) from score where student_id = 1)
112  
113  
114 15、删除学习“叶平”老师课的score表记录；
115  
116     delete from score where course_id in (
117         select cid from course left join teacher on course.teacher_id = teacher.tid where teacher.name = ‘叶平‘
118     )
119  
120 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；
121     思路：
122         由于insert 支持 
123                 inset into tb1(xx,xx) select x1,x2 from tb2;
124         所有，获取所有没上过002课的所有人，获取002的平均成绩
125  
126     insert into score(student_id, course_id, num) select sid,2,(select avg(num) from score where course_id = 2)
127     from student where sid not in (
128         select student_id from score where course_id = 2
129     )
130      
131 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；
132     select sc.student_id,
133         (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,
134         (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,
135         (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,
136         count(sc.course_id),
137         avg(sc.num)
138     from score as sc
139     group by student_id desc        
140  
141 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；
142      
143     select course_id, max(num) as max_num, min(num) as min_num from score group by course_id;
144  
145 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；
146     思路：case when .. then
147     select course_id, avg(num) as avgnum,sum(case when score.num > 60 then 1 else 0 END)/count(1)*100 as percent from score group by course_id order by avgnum asc,percent desc;
148  
149 20、课程平均分从高到低显示（现实任课老师）；
150  
151     select avg(if(isnull(score.num),0,score.num)),teacher.tname from course
152     left join score on course.cid = score.course_id
153     left join teacher on course.teacher_id = teacher.tid
154  
155     group by score.course_id
156  

                        

                            

                                
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