表结构及基本测试数据
#创建表及插入记录 CREATE TABLE class ( cid int(11) NOT NULL AUTO_INCREMENT, caption varchar(32) NOT NULL, PRIMARY KEY (cid) ) ENGINE=InnoDB CHARSET=utf8; INSERT INTO class VALUES (1, '三年二班'), (2, '三年三班'), (3, '一年二班'), (4, '二年九班'); 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 DEFAULT CHARSET=utf8; INSERT INTO course VALUES (1, '生物', 1), (2, '物理', 2), (3, '体育', 3), (4, '美术', 2); 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 DEFAULT CHARSET=utf8; 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); 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 DEFAULT CHARSET=utf8; 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'); CREATE TABLE teacher( tid int(11) NOT NULL AUTO_INCREMENT, tname varchar(32) NOT NULL, PRIMARY KEY (tid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; 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');
需要完成的查询问题:
1、查询所有的课程的名称以及对应的任课老师姓名
2、查询学生表中男女生各有多少人
3、查询物理成绩等于100的学生的姓名
4、查询平均成绩大于八十分的同学的姓名和平均成绩
5、查询所有学生的学号,姓名,选课数,总成绩
6、 查询姓李老师的个数
7、 查询没有报李平老师课的学生姓名
8、 查询物理课程比生物课程高的学生的学号
9、 查询没有同时选修物理课程和体育课程的学生姓名
10、查询挂科超过两门(包括两门)的学生姓名和班级、查询选修了所有课程的学生姓名
12、查询李平老师教的课程的所有成绩记录
13、查询全部学生都选修了的课程号和课程名
14、查询每门课程被选修的次数
15、查询之选修了一门课程的学生姓名和学号
16、查询所有学生考出的成绩并按从高到低排序(成绩去重)
17、查询平均成绩大于85的学生姓名和平均成绩
18、查询生物成绩不及格的学生姓名和对应生物分数
19、查询在所有选修了李平老师课程的学生中,这些课程(李平老师的课程,不是所有课程)平均成绩最高的学生姓名
参考解决答案:
1、查询所有的课程的名称以及对应的任课老师姓名
SELECT course.cname, teacher.tname FROM course INNER JOIN teacher ON course.teacher_id = teacher.tid;
2、查询学生表中男女生各有多少人
SELECT gender 性别, count(1) 人数 FROM student GROUP BY gender;
3、查询物理成绩等于100的学生的姓名
SELECT student.sname FROM student WHERE sid IN ( SELECT student_id FROM score INNER JOIN course ON score.course_id = course.cid WHERE course.cname = '物理' AND score.num = 100 );
4、查询平均成绩大于八十分的同学的姓名和平均成绩
SELECT student.sname, t1.avg_num FROM student INNER JOIN ( SELECT student_id, avg(num) AS avg_num FROM score GROUP BY student_id HAVING avg(num) > 80 ) AS t1 ON student.sid = t1.student_id;
5、查询所有学生的学号,姓名,选课数,总成绩(注意:对于那些没有选修任何课程的学生也算在内)
SELECT student.sid, student.sname, t1.course_num, t1.total_num FROM student LEFT JOIN ( SELECT student_id, COUNT(course_id) course_num, sum(num) total_num FROM score GROUP BY student_id ) AS t1 ON student.sid = t1.student_id;
6、 查询姓李老师的个数
SELECT count(tid) FROM teacher WHERE tname LIKE '李%';
7、 查询没有报李平老师课的学生姓名(找出报名李平老师课程的学生,然后取反就可以)
SELECT student.sname FROM student WHERE sid NOT IN ( SELECT DISTINCT student_id FROM score WHERE course_id IN ( SELECT course.cid FROM course INNER JOIN teacher ON course.teacher_id = teacher.tid WHERE teacher.tname = '李平老师' ) );
面试必备杀技:SQL查询专项训练(二)https://developer.aliyun.com/article/1424273