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)
本文标题: MySQL中的max()函数使用教程
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