MySQL中的max()函数使用教程

时间:2022-05-28 02:28:20

MySQLmax()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:

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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:

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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:

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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:

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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)