数据库：
class：
course：
student：
teacher：
score：
/* 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;
1. 成绩表中所有大于60分的数据
SELECT * from score where num>60;
2. 查询每个老师教多少门课
SELECT teacher_id,COUNT(cid) FROM course GROUP BY teacher_id;
3. 列出课程与对应老师
SELECT * FROM course LEFT JOIN teacher on course.teacher_id=teacher.tid;
4. 列出学生与对应班级
SELECT * FROM student LEFT JOIN class on student.class_id=class.cid;
5. 列出男生的个数和女生的个数
SELECT gender,COUNT(gender) from student GROUP BY gender;
6. 查询“生物”课程比“物理”课程成绩高的所有学生的学号
先拿到所有的生物成绩SELECT score.sid,score.student_id,course.cname,score.num from score LEFT JOIN course ON score.course_id=course.cid WHERE course.cname='生物';
在拿到所有的物理成绩SELECT score.sid,score.student_id,course.cname,score.num from score LEFT JOIN course ON score.course_id=course.cid WHERE course.cname='物理';
接着输出生物成绩大于物理成绩的数据SELECT * FROM ( SELECT score.sid, score.student_id, course.cname, score.num FROM score LEFT JOIN course ON score.course_id = course.cid WHERE course.cname = '生物' ) AS A INNER JOIN ( SELECT score.sid, score.student_id, course.cname, score.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;
最后，把* 改为A.student_id 即可SELECT A.student_id FROM ( SELECT score.sid, score.student_id, course.cname, score.num FROM score LEFT JOIN course ON score.course_id = course.cid WHERE course.cname = '生物' ) AS A INNER JOIN ( SELECT score.sid, score.student_id, course.cname, score.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;
7. 查询平均成绩大于60分的同学的学号、姓名和平均成绩
select student_id,student.sname,avg(num) from score LEFT JOIN student ON score.student_id=student.sid GROUP BY student_id HAVING AVG(num)>60;
用临时表做：
SELECT B.student_id,student.sname,B.avg_num from (select student_id,avg(num) as avg_num from score GROUP BY student_id HAVING AVG(num)>60) as B LEFT join student on B.student_id=student.sid;
8. 查询所有同学的学号、姓名、选课数、总成绩
select student.sid,student.sname,COUNT(score.course_id),sum(score.num) from student LEFT JOIN score ON student.sid=score.student_id GROUP BY student.sid;
9. 查询姓“李”的老师的个数
select count(tid) from teacher where tname like '李%';
10. 查询没学过“李平”老师课的同学的学号、姓名
先查询选过李平老师课的学生IDSELECT student_id FROM score WHERE course_id IN ( SELECT course.cid FROM teacher LEFT JOIN course ON teacher.tid = course.teacher_id WHERE teacher.tname = '李平老师' ) GROUP BY student_id
最后，从学生表里面选出没学过李平老师的课的数据
SELECT student.sid, student.sname FROM student WHERE sid NOT IN ( SELECT student_id FROM score WHERE course_id IN ( SELECT course.cid FROM teacher LEFT JOIN course ON teacher.tid = course.teacher_id WHERE teacher.tname = '李平老师' ) GROUP BY student_id )
