MySQL练习题参考答案

Posted 2020-11-20 amyleell

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• 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：

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/*
 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;

第一题答案

  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  
157  
158 21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
159     select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
160     (
161     select
162         sid,
163         (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
164         (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 3,1) as second_num
165     from
166         score as s1
167     ) as T
168     on score.sid =T.sid
169     where score.num <= T.first_num and score.num >= T.second_num
170  
171 22、查询每门课程被选修的学生数；
172      
173     select course_id, count(1) from score group by course_id;
174  
175 23、查询出只选修了一门课程的全部学生的学号和姓名；
176     select student.sid, student.sname, count(1) from score
177  
178     left join student on score.student_id  = student.sid
179  
180      group by course_id having count(1) = 1
181  
182  
183 24、查询男生、女生的人数；
184     select * from
185     (select count(1) as man from student where gender=‘男‘) as A ,
186     (select count(1) as feman from student where gender=‘女‘) as B
187  
188 25、查询姓“张”的学生名单；
189     select sname from student where sname like ‘张%‘;
190  
191 26、查询同名同姓学生名单，并统计同名人数；
192  
193     select sname,count(1) as count from student group by sname;
194  
195 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；
196     select course_id,avg(if(isnull(num), 0 ,num)) as avg from score group by course_id order by avg     asc,course_id desc;
197  
198 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；
199  
200     select student_id,sname, avg(if(isnull(num), 0 ,num)) from score left join student on score.student_id = student.sid group by student_id;
201  
202 29、查询课程名称为“数学”，且分数低于60的学生姓名和分数；
203  
204     select student.sname,score.num from score
205     left join course on score.course_id = course.cid
206     left join student on score.student_id = student.sid
207     where score.num < 60 and course.cname = ‘生物‘
208  
209 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；
210     select * from score where score.student_id = 3 and score.num > 80
211  
212 31、求选了课程的学生人数
213  
214     select count(distinct student_id) from score
215  
216     select count(c) from (
217         select count(student_id) as c from score group by student_id) as A
218  
219 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；
220      
221     select sname,num from score
222     left join student on score.student_id = student.sid
223     where score.course_id in (select course.cid from course left join teacher on course.teacher_id = teacher.tid where tname=‘张磊老师‘) order by num desc limit 1;
224  
225 33、查询各个课程及相应的选修人数；
226     select course.cname,count(1) from score
227     left join course on score.course_id = course.cid
228     group by course_id;
229  
230  
231 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；
232     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;
233  
234 35、查询每门课程成绩最好的前两名；
235  
236     select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
237     (
238     select
239         sid,
240         (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
241         (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 1,1) as second_num
242     from
243         score as s1
244     ) as T
245     on score.sid =T.sid
246     where score.num <= T.first_num and score.num >= T.second_num
247  
248 36、检索至少选修两门课程的学生学号；
249     select student_id from score group by student_id having count(student_id) > 1
250  
251 37、查询全部学生都选修的课程的课程号和课程名；
252     select course_id,count(1) from score group by course_id having count(1) = (select count(1) from student);
253  
254 38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；
255     select student_id,student.sname from score
256     left join student on score.student_id = student.sid
257     where score.course_id not in (
258         select cid from course left join teacher on course.teacher_id = teacher.tid where tname = ‘张磊老师‘
259     )
260     group by student_id
261  
262 39、查询两门以上不及格课程的同学的学号及其平均成绩；
263  
264     select student_id,count(1) from score where num < 60 group by student_id having count(1) > 2
265  
266 40、检索“004”课程分数小于60，按分数降序排列的同学学号；
267     select student_id from score where num< 60 and course_id = 4 order by num desc;
268  
269 41、删除“002”同学的“001”课程的成绩；
270     delete from score where course_id = 1 and student_id = 2