MySQL中的max()函数使用教程

数据库  /  管理员 发布于 6年前   515

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)