MySQL AVG 函数用于查找各种记录中某个字段的平均值。

要了解 AVG 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,假设基于上表您要计算所有dialy_typing_pages的平均值,那么您可以使用以下命令进行计算-

mysql> SELECT AVG(daily_typing_pages)
   -> FROM employee_tbl;
+-------------------------+
| AVG(daily_typing_pages) |
+-------------------------+
|         230.0000        |
+-------------------------+
1 row in set (0.03 sec)

您可以使用 GROUP BY 子句取平均各种记录集。下面的Example将平均获取与一个人相关的所有记录,并且每个人的平均输入页面数将为平均。

mysql> SELECT name, AVG(daily_typing_pages)
   -> FROM employee_tbl GROUP BY name;
+------+-------------------------+
| name | AVG(daily_typing_pages) |
+------+-------------------------+
| Jack |        135.0000         |
| Jill |        220.0000         |
| John |        250.0000         |
| Ram  |        220.0000         |
| Zara |        325.0000         |
+------+-------------------------+
5 rows in set (0.20 sec)

参考链接

https://www.learnfk.com/mysql/mysql-avg-function.html