MySQL的max()函数是用来找出一个记录集中的最大值记录。
要了解MAX功能考虑的EMPLOYEE_TBL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，假设根据上述要取表中daily_typing_pages的最大值值，简单地使用下面的命令：
mysql> SELECT MAX(daily_typing_pages) -> FROM employee_tbl; +-------------------------+ | MAX(daily_typing_pages) | +-------------------------+ | 350 | +-------------------------+ 1 row in set (0.00 sec)
可以找到所有的记录，最大值为每名使用GROUP BY子句如下：
mysql> SELECT id, name, work_date, MAX(daily_typing_pages) -> FROM employee_tbl GROUP BY name; +------+------+------------+-------------------------+ | id | name | work_date | MAX(daily_typing_pages) | +------+------+------------+-------------------------+ | 3 | Jack | 2007-05-06 | 170 | | 4 | Jill | 2007-04-06 | 220 | | 1 | John | 2007-01-24 | 250 | | 2 | Ram | 2007-05-27 | 220 | | 5 | Zara | 2007-06-06 | 350 | +------+------+------------+-------------------------+ 5 rows in set (0.00 sec)
也可以使用MIN函数及MAX功能找到的最低值，试试下面的例子：
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)
