MySql練習題參考答案
/* 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', '體育', '3'), ('4', '美術', '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', '鋼蛋'), ('3', '男', '1', '張三'), ('4', '男', '1', '張一'), ('5', '女', '1', '張二'), ('6', '男', '1', '張四'), ('7', '女', '2', '鐵錘'), ('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', '劉三'), ('14', '男', '3', '劉一'), ('15', '女', '3', '劉二'), ('16', '男', '3', '劉四'); 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', '張磊老師'), ('2', '李平老師'), ('3', '劉海燕老師'), ('4', '朱雲海老師'), ('5', '李傑老師'); COMMIT; SET FOREIGN_KEY_CHECKS = 1; 表結構和數據
import pymysql conn = pymysql.connect(host='127.0.0.1', user='root', password='', database='mysql_test', charset='utf8') cursor = conn.cursor() # 插入班級表 klass = '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;' klass_info = "INSERT INTO `class` VALUES ('1', '三年二班'), ('2', '三年三班'), ('3', '一年二班'), ('4', '二年九班');" # 學生表 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`),CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`) on delete cascade on update cascade) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8;" student_info = "INSERT INTO `student` VALUES ('2', '女', '1', '鋼蛋'), ('3', '男', '1', '張三'), ('4', '男', '1', '張一'), ('5', '女', '1', '張二'), ('6', '男', '1', '張四'), ('7', '女', '2', '鐵錘'), ('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', '劉三'), ('14', '男', '3', '劉一'), ('15', '女', '3', '劉二'), ('16', '男', '3', '劉四');" # 教師表 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;" teacher_info = "INSERT INTO `teacher` VALUES ('1', '張磊老師'), ('2', '李平老師'), ('3', '劉海燕老師'), ('4', '朱雲海老師'), ('5', '李傑老師');" # 課程表 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`), CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`) on delete cascade on update cascade) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;" course_info = "INSERT INTO `course` VALUES (1, '生物', 1), (2, '物理', 2), (3, '體育', 3), (4, '美術', 2);" # 分數表 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`), CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`) on delete cascade on update cascade , CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`) on delete cascade on update cascade) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8;" score_info = "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');" # cursor.execute(score) # cursor.execute(score_info) sql = "select student_id,avg(num) from score group by student_id having avg(num) > 60" cursor.execute(sql) print(cursor.fetchall()) conn.commit()
練習題答案：
2、查詢「生物」課程比「物理」課程成績高的全部學生的學號； 思路： 獲取全部有生物課程的人（學號，成績） - 臨時表 獲取全部有物理課程的人（學號，成績） - 臨時表 根據【學號】鏈接兩個臨時表： 學號 物理成績 生物成績 而後再進行篩選 select A.student_id,sw,ty from (select student_id,num as sw from score left join course on score.course_id = course.cid where course.cname = '生物') as A left join (select student_id,num as ty from score left join course on score.course_id = course.cid where course.cname = '體育') as B on A.student_id = B.student_id where sw > if(isnull(ty),0,ty); 3、查詢平均成績大於60分的同窗的學號和平均成績； 思路： 根據學生分組，使用avg獲取平均值，經過having對avg進行篩選 select student_id,avg(num) from score group by student_id having avg(num) > 60 4、查詢全部同窗的學號、姓名、選課數、總成績； select score.student_id,sum(score.num),count(score.student_id),student.sname from score left join student on score.student_id = student.sid group by score.student_id 5、查詢姓「李」的老師的個數； select count(tid) from teacher where tname like '李%' select count(1) from (select tid from teacher where tname like '李%') as B 6、查詢沒學過「葉平」老師課的同窗的學號、姓名； 思路： 先查到「李平老師」老師教的全部課ID 獲取選過課的全部學生ID 學生表中篩選 select * from student where sid not in ( select DISTINCT student_id from score where score.course_id in ( select cid from course left join teacher on course.teacher_id = teacher.tid where tname = '李平老師' ) ) 七、查詢學過「001」而且也學過編號「002」課程的同窗的學號、姓名； 思路： 先查到既選擇001又選擇002課程的全部同窗 根據學生進行分組，若是學生數量等於2表示，兩門均已選擇 select student_id,sname from (select student_id,course_id from score where course_id = 1 or course_id = 2) as B left join student on B.student_id = student.sid group by student_id HAVING count(student_id) > 1 8、查詢學過「葉平」老師所教的全部課的同窗的學號、姓名； 同上，只不過將001和002變成 in (葉平老師的全部課) 九、查詢課程編號「002」的成績比課程編號「001」課程低的全部同窗的學號、姓名； 同第1題 10、查詢有課程成績小於60分的同窗的學號、姓名； select sid,sname from student where sid in ( select distinct student_id from score where num < 60 ) 11、查詢沒有學全全部課的同窗的學號、姓名； 思路： 在分數表中根據學生進行分組，獲取每個學生選課數量 若是數量 == 總課程數量，表示已經選擇了全部課程 select student_id,sname from score left join student on score.student_id = student.sid group by student_id HAVING count(course_id) = (select count(1) from course) 十二、查詢至少有一門課與學號爲「001」的同窗所學相同的同窗的學號和姓名； 思路： 獲取 001 同窗選擇的全部課程 獲取課程在其中的全部人以及全部課程 根據學生篩選，獲取全部學生信息 再與學生錶鏈接，獲取姓名 select student_id,sname, count(course_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 1三、查詢至少學過學號爲「001」同窗全部課的其餘同窗學號和姓名； 先找到和001的學過的全部人 而後個數 ＝ 001全部學科 ＝＝》 其餘人可能選擇的更多 select student_id,sname, count(course_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(course_id) ＝ (select count(course_id) from score where student_id = 1) 1四、查詢和「002」號的同窗學習的課程徹底相同的其餘同窗學號和姓名； 個數相同 002學過的也學過 select student_id,sname from score left join student on score.student_id = student.sid where student_id in ( 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) ) 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) 15、刪除學習「葉平」老師課的score表記錄； delete from score where course_id in ( select cid from course left join teacher on course.teacher_id = teacher.tid where teacher.name = '葉平' ) 1六、向SC表中插入一些記錄，這些記錄要求符合如下條件：①沒有上過編號「002」課程的同窗學號；②插入「002」號課程的平均成績； 思路： 因爲insert 支持 inset into tb1(xx,xx) select x1,x2 from tb2; 全部，獲取全部沒上過002課的全部人，獲取002的平均成績 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、按平均成績從低到高 顯示全部學生的「語文」、「數學」、「英語」三門的課程成績，按以下形式顯示： 學生ID,語文,數學,英語,有效課程數,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 = "體育" and score.student_id=sc.student_id) as ty, count(sc.course_id), avg(sc.num) from score as sc group by student_id desc 18、查詢各科成績最高和最低的分：以以下形式顯示：課程ID，最高分，最低分； select course_id, max(num) as max_num, min(num) as min_num from score group by course_id; 19、按各科平均成績從低到高和及格率的百分數從高到低順序； 思路：case when .. then 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; 20、課程平均分從高到低顯示（現實任課老師）； select avg(if(isnull(score.num),0,score.num)),teacher.tname from course left join score on course.cid = score.course_id left join teacher on course.teacher_id = teacher.tid group by score.course_id 21、查詢各科成績前三名的記錄:(不考慮成績並列狀況) 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、查詢每門課程被選修的學生數； select course_id, count(1) from score group by course_id; 23、查詢出只選修了一門課程的所有學生的學號和姓名； select student.sid, student.sname, count(1) from score left join student on score.student_id = student.sid group by course_id having count(1) = 1 24、查詢男生、女生的人數； select COUNT(1),gender from student GROUP BY gender
25、查詢姓「張」的學生名單； select sname from student where sname like '張%'; 26、查詢同名同姓學生名單，並統計同名人數； select sname,count(1) as count from student group by sname; 27、查詢每門課程的平均成績，結果按平均成績升序排列，平均成績相同時，按課程號降序排列； 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、查詢平均成績大於85的全部學生的學號、姓名和平均成績；
select student_id,sname, avg(if(isnull(num), 0 ,num)) as avg from score left join student on score.student_id = student.sidpython
group by student_id HAVING avg > 85;mysql
29、查詢課程名稱爲「數學」，且分數低於60的學生姓名和分數； select student.sname,score.num from score left join course on score.course_id = course.cid left join student on score.student_id = student.sid where score.num < 60 and course.cname = '生物' 30、查詢課程編號爲003且課程成績在80分以上的學生的學號和姓名； select * from score where score.student_id = 3 and score.num > 80 31、求選了課程的學生人數 select count(distinct student_id) from score select count(c) from ( select count(student_id) as c from score group by student_id) as A 32、查詢選修「楊豔」老師所授課程的學生中，成績最高的學生姓名及其成績； select sname,num 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 tname='張磊老師') order by num desc limit 1; 33、查詢各個課程及相應的選修人數； select course.cname,count(1) from score left join course on score.course_id = course.cid group by course_id; 34、查詢不一樣課程但成績相同的學生的學號、課程號、學生成績； 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、查詢每門課程成績最好的前兩名； 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、檢索至少選修兩門課程的學生學號； select student_id from score group by student_id having count(student_id) > 1 37、查詢所有學生都選修的課程的課程號和課程名； select course_id,count(1) from score group by course_id having count(1) = (select count(1) from student); 38、查詢沒學過「葉平」老師講授的任一門課程的學生姓名； 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 = '張磊老師' ) group by student_id 39、查詢兩門以上不及格課程的同窗的學號及其平均成績； select student_id,count(1) from score where num < 60 group by student_id having count(1) > 2 40、檢索「004」課程分數小於60，按分數降序排列的同窗學號； select student_id from score where num< 60 and course_id = 4 order by num desc; 4一、刪除「002」同窗的「001」課程的成績； delete from score where course_id = 1 and student_id = 2