mysql练习题参考答案
/* 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; 表结构和数据
import pymysql conn = pymysql.connect(host=\'127.0.0.1\', user=\'root\', password=\'\', database=\'mysql_test\', charset=\'utf8\') cursor = conn.cursor() # 插入班级表 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\');" # 学生表 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\', \'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\');" # 教师表 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\', \'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\');" # 课程表 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, \'体育\', 3), (4, \'美术\', 2);" # 分数表 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()
练习题答案：
2、查询“生物”课程比“物理”课程成绩高的所有学生的学号； 思路： 获取所有有生物课程的人（学号，成绩） - 临时表 获取所有有物理课程的人（学号，成绩） - 临时表 根据【学号】连接两个临时表： 学号 物理成绩 生物成绩 然后再进行筛选 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 = \'体育\') as B on A.student_id = B.student_id where sw > if(isnull(ty),0,ty); 3、查询平均成绩大于60分的同学的学号和平均成绩； 思路： 根据学生分组，使用avg获取平均值，通过having对avg进行筛选 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 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、查询姓“李”的老师的个数； select count(tid) from teacher where tname like \'李%\' select count(1) from (select tid from teacher where tname like \'李%\') as B 6、查询没学过“叶平”老师课的同学的学号、姓名； 思路： 先查到“李平老师”老师教的所有课ID 获取选过课的所有学生ID 学生表中筛选 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； 思路： 先查到既选择001又选择002课程的所有同学 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 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、查询学过“叶平”老师所教的所有课的同学的学号、姓名； 同上，只不过将001和002变成 in (叶平老师的所有课) 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； 同第1题 10、查询有课程成绩小于60分的同学的学号、姓名； select sid,sname from student where sid in ( select distinct 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； 思路： 在分数表中根据学生进行分组，获取每一个学生选课数量 如果数量 == 总课程数量，表示已经选择了所有课程 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) 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； 思路： 获取 001 同学选择的所有课程 获取课程在其中的所有人以及所有课程 根据学生筛选，获取所有学生信息 再与学生表连接，获取姓名 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 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； 先找到和001的学过的所有人 然后个数 ＝ 001所有学科 ＝＝》 其他人可能选择的更多 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) 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； 个数相同 002学过的也学过 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(以上是关于mysql练习题的主要内容，如果未能解决你的问题，请参考以下文章
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