复杂sql语句练习

复杂sql语句练习

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
        teacher INNER JOIN course ON teacher.tid = course.teacher_id
        
        cname   tname
        生物      张磊老师
        物理      李平老师
        美术      李平老师
        体育      刘海燕老师

2.查询平均成绩大于80分的同学的姓名和平均成绩
SELECT
    student.sname,
    t1.ag 
FROM
    student
    INNER JOIN (
    SELECT
        score.student_id,
        AVG( score.num ) AS ag 
    FROM
        score 
    GROUP BY
        score.student_id 
    HAVING
        AVG( score.num ) > 80 
    ) AS t1 ON t1.student_id = student.sid;
    sname       ag
    张三          82.2500
    刘三          87.0000

3.查询没有报李平老师课的学生姓名
    SELECT
    sname 
FROM
    student 
WHERE
    student.sid NOT IN (
    SELECT
        student_id 
    FROM
        score 
    WHERE
        course_id IN ( SELECT DISTINCT cid FROM teacher INNER JOIN course ON teacher.tid = course.teacher_id WHERE tname = '李平老师' ) 
    );
    sanme
    刘三
    刘一
    刘二
    刘四

4.查询没有同时选修物理课程和体育课程的学生姓名
    SELECT
    sname 
FROM
    student 
WHERE
    sid IN (
    SELECT
        student_id 
    FROM
        (
            ( SELECT * FROM score INNER JOIN course ON cid = course_id WHERE course.cname = '物理' OR course.cname = '体育' ) AS t1 
        ) 
    GROUP BY
        student_id 
    HAVING
        COUNT( student_id ) = 1 
    );
    sname
    理解
    钢蛋
    刘三

5.查询挂科超过两门（包括两门）的学生姓名和班级
    SELECT
    t2.caption,
    t2.sname 
FROM
    ( ( SELECT * FROM class INNER JOIN student ON cid = class_id ) AS t2 ) 
WHERE
    sname IN (
    SELECT
        sname 
    FROM
        student 
    WHERE
        sid IN ( SELECT student_id FROM score WHERE num < 60 GROUP BY student_id HAVING COUNT( student_id ) >= 2 ) 
    );
    caption     sname
    三年二班        理解