要了解AVG功能考虑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)
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现在，假设根据上面的表，要计算所有的dialy_typing_pages的平均值，那么可以通过使用下面的命令：
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mysql> SELECT AVG(daily_typing_pages)
-> FROM employee_tbl;
+-------------------------+
| AVG(daily_typing_pages) |
+-------------------------+
| 230.0000 |
+-------------------------+
1 row in set (0.03 sec)
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可以把平均使用GROUP BY子句设置的各种记录。下面的例子将采取平均到一个人的所有相关的记录，每个人的平均页打印纸。
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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)
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