练习1--查询"01"课程比"02"课程成绩高的学生的信息及课程分数

查询"01"课程比"02"课程成绩高的学生的信息及课程分数 

-- 解法一：

    select
        s1.*,
        s2.01_score,
        s2.02_score
    from
        student s1,
        (
            select t1.s_id as s_id,
            t1.s_score as 01_score,
            t2.s_score as 02_score
        from
            score t1,
            score t2
        where
            t1.s_id = t2.s_id
            and t1.c_id = '01'
            and t2.c_id = '02'
            and t1.s_score > t2.s_score ) s2
    where
        s1.s_id = s2.s_id;

 

--参考解法

    select
        a.* ,
        b.s_score as 01 _score,
        c.s_score as 02 _score
    from
        student a
    join score b on
        a.s_id = b.s_id
        and b.c_id = '01'
    left join score c on
        a.s_id = c.s_id
        and c.c_id = '02'
        or c.c_id = null
    where
        b.s_score>c.s_score;

-- 2019/04/15