MySQL MAX 函数

  • MAX 函数

    MySQL MAX函数用于在记录集中找出最大值的记录。要了解MAX函数,请考虑一个employee_tbl表,该表具有以下记录-
    mysql> 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,假设基于上表您要获取daily_typing_pages的最大值,那么您可以使用以下命令简单地做到这一点:
    mysql> SELECT MAX(daily_typing_pages)
       -> FROM employee_tbl;
    +-------------------------+
    | MAX(daily_typing_pages) |
    +-------------------------+
    |           350           |
    +-------------------------+
    1 row in set (0.00 sec)
    您可以使用GROUP BY子句找到每个名称具有最大值的所有记录,如下所示-
    mysql> SELECT id, name, MAX(daily_typing_pages)
       -> FROM employee_tbl GROUP BY name;
    +------+------+-------------------------+
    |  id  | name | MAX(daily_typing_pages) |
    +------+------+-------------------------+
    |   3  | Jack |           170           |
    |   4  | Jill |           220           |
    |   1  | John |           250           |
    |   2  | Ram  |           220           |
    |   5  | Zara |           350           |
    +------+------+-------------------------+
    5 rows in set (0.00 sec)
    您也可以将MIN 函数和MAX 函数一起使用以找出最小值。尝试以下示例-
    mysql> SELECT MIN(daily_typing_pages) least, MAX(daily_typing_pages) max
       -> FROM employee_tbl;
    +-------+------+
    | least |  max |
    +-------+------+
    |  100  |  350 |
    +-------+------+
    1 row in set (0.01 sec)