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  • SQL查询有两门以上不及格的学生及查询出全部及格的学生

    1、表结构:

    /*学生*/
    create table student(
    sno int not null primary key,
    sname varchar(10)
    );
    /*课程*/
    create table center(
    cno int not null primary key,
    cname varchar(10)
    );
    /*分数*/
    create table sgrade(
    sno int ,
    cno int ,
    sgrade int
    );

    2、插入数据:

    insert into student values(11,'a');
    insert into student values(12,'b');
    insert into student values(13,'c')
    
    insert into center values(21,'aa');
    insert into center values(22,'bb');
    insert into center values(23,'cc')
    
    insert into sgrade values(11,21,54);
    insert into sgrade values(12,22,57);
    insert into sgrade values(11,21,51);
    insert into sgrade values(12,21,36);
    insert into sgrade values(11,21,28);
    insert into sgrade values(12,22,42);
    insert into sgrade values(11,21,59)
    insert into sgrade values(11,21,79);
    insert into sgrade values(12,22,85);
    insert into sgrade values(11,21,90);
    insert into sgrade values(12,21,96);
    insert into sgrade values(11,21,98);
    insert into sgrade values(12,22,94);
    insert into sgrade values(11,21,99)

    3、查询出有两门以上不及格的学生:

    SELECT s.sno,s.sname 
        from student s
        LEFT JOIN sgrade g on s.sno=g.sno
    WHERE g.sgrade<60
    GROUP BY s.sno HAVING COUNT(s.sno)>2

    4、查询出全部及格的学生:

    SELECT * FROM student WHERE sno not in (
        SELECT s.sno
            from student s
            LEFT JOIN sgrade g on s.sno=g.sno
        WHERE g.sgrade<60 
    )
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  • 原文地址:https://www.cnblogs.com/java-zzl/p/9739976.html
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