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)