【mysql】成绩单表，找到所有成绩都不及格的所有人

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/a19990412/article/details/83503626

简述

这里考虑到两种情况。如果人的信息和成绩的信息都在一个表上，和在不同的表上的。

在一个表上的时候

先看看数据

mysql> select * from sc;
+---------+-----+-------+
| sno     | cno | grade |
+---------+-----+-------+
| 2005001 | 1   | 87.00 |
| 2005001 | 2   | 67.00 |
| 2005001 | 3   | 90.00 |
| 2005002 | 2   | 95.00 |
| 2005003 | 3   | 88.00 |
| 2005003 | 7   |  NULL |
| 2005010 | 1   | 87.00 |
| 2005010 | 2   |  NULL |
| 2005010 | 3   | 80.00 |
| 2005010 | 4   | 87.00 |
| 2005010 | 6   | 85.00 |
| 2005011 | 1   | 52.00 |
| 2005011 | 2   | 47.00 |
| 2005011 | 3   | 53.00 |
| 2005011 | 5   | 45.00 |
| 2005012 | 1   | 84.00 |
| 2005012 | 3   |  NULL |
| 2005012 | 4   | 67.00 |
| 2005012 | 5   | 81.00 |
| 2005012 | 7   |  NULL |
+---------+-----+-------+
20 rows in set (0.00 sec)

查询方法

mysql> select sno from sc
    -> group by sno
    -> having max(grade) < 60;
+---------+
| sno     |
+---------+
| 2005011 |
+---------+
1 row in set (0.00 sec)

在两张表上

比如，还是基于刚刚的问题，我这时候需要获得这个编号所对应的人的名字和信息。

mysql> select * from student s
    -> where s.sno in (
    -> select sno from sc
    -> group by sno
    -> having max(grade) < 60
    -> );
+---------+--------+------+------+-------+
| sno     | sname  | sage | ssex | sdept |
+---------+--------+------+------+-------+
| 2005011 | 张丽萍 |   19 | 女   | Ch    |
+---------+--------+------+------+-------+
1 row in set (0.01 sec)

mysql>

如果想要基于这张表还创建一个新的表。

mysql> create table ts
    -> ( select * from student s
    -> where s.sno in (
    -> select sno from sc
    -> group by sno
    -> having max(grade) < 60
    -> ));
Query OK, 1 row affected (0.18 sec)
Records: 1  Duplicates: 0  Warnings: 0

看看新表的结果

mysql> select * from ts;
+---------+--------+------+------+-------+
| sno     | sname  | sage | ssex | sdept |
+---------+--------+------+------+-------+
| 2005011 | 张丽萍 |   19 | 女   | Ch    |
+---------+--------+------+------+-------+
1 row in set (0.00 sec)