SQL平均值函数 avg()函数

AVG() 函数返回数值列的平均值。

语法结构：

SELECT AVG(column_name) FROM table_name

avg()函数实例

实例数据

+-----+---------+-------+------------+
| aid | site_id | count | date       |
+-----+---------+-------+------------+
|   1 |       1 |    45 | 2016-05-10 |
|   2 |       3 |   100 | 2016-05-13 |
|   3 |       1 |   230 | 2016-05-14 |
|   4 |       2 |    10 | 2016-05-14 |
|   5 |       5 |   205 | 2016-05-14 |
|   6 |       4 |    13 | 2016-05-15 |
|   7 |       3 |   220 | 2016-05-15 |
|   8 |       5 |   545 | 2016-05-16 |
|   9 |       3 |   201 | 2016-05-17 |
+-----+---------+-------+------------+

#查询count列的平均值
SELECT AVG(count) AS CountAverage FROM access_log;

查询结果：

查询count值大于平均值的数据

SELECT site_id, count FROM access_log WHERE count > (SELECT AVG(count) FROM access_log);