sql minus函数 SQL MIN 函数

SQL MIN 函数

MIN函数用于找出记录集中具有最大值的记录。

要理解 MIN 函数，请考虑 employee_tbl 表，表中记录如下所示：

    SQL> SELECT * FROM employee_tbl;
    +------+------+------------+--------------------+
    | id   | name | work_date  | daily_typing_pages |
    +------+------+------------+--------------------+
    |    1 | John | 2007-01-24 |                250 |
    |    2 | Ram  | 2007-05-27 |                220 |
    |    3 | Jack | 2007-05-06 |                170 |
    |    3 | Jack | 2007-04-06 |                100 |
    |    4 | Jill | 2007-04-06 |                220 |
    |    5 | Zara | 2007-06-06 |                300 |
    |    5 | Zara | 2007-02-06 |                350 |
    +------+------+------------+--------------------+
    7 rows in set (0.00 sec)

现在，假设你想要获取 daily_typing_pages 的最小值，那么你可以用如下命令来达到目的：

    SQL> SELECT MIN(daily_typing_pages)
        -> FROM employee_tbl;
    +-------------------------+
    | MIN(daily_typing_pages) |
    +-------------------------+
    |                     100 |
    +-------------------------+
    1 row in set (0.00 sec)

你还可以使用 GROUP BY 子句，为每个名字（name）找出 daily_typing_pages 的最小值：

    SQL> SELECT id, name, work_date, MIN(daily_typing_pages)
        -> FROM employee_tbl GROUP BY name;
    +------+------+-------------------------+
    | id   | name | MIN(daily_typing_pages) |
    +------+------+-------------------------+
    |    3 | Jack |                     100 |
    |    4 | Jill |                     220 |
    |    1 | John |                     250 |
    |    2 | Ram  |                     220 |
    |    5 | Zara |                     300 |
    +------+------+-------------------------+
    5 rows in set (0.00 sec)