MySQL Max()函數

MySQL Max() 函數是用來找出記錄集中最大值的記錄。

要理解 Max() 函數，考慮 employee_tbl 表，它是具有以下記錄：

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)

現在，假設想獲取上表中daily_typing_pages的字段的最大值對應的記錄， 那麼可以簡單地使用下面的命令：

mysql> SELECT MAX(daily_typing_pages)
    -> FROM employee_tbl;
+-------------------------+
| MAX(daily_typing_pages) |
+-------------------------+
|                     350 |
+-------------------------+
1 row in set (0.00 sec)

可以使用GROUP BY子句找到所有記錄中最大值對應的名字如下：

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)

可以使用 Min() 函數和 Max() 函數一起，找出最小值和最大值。試試下面的例子：

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)