Question

description

Syntax

AVG([DISTINCT] expr)

用于返回选中字段的平均值

可选字段DISTINCT参数可以用来返回去重平均值

example

mysql> SELECT datetime, AVG(cost_time) FROM log_statis group by datetime;
+---------------------+--------------------+
| datetime            | avg(`cost_time`)   |
+---------------------+--------------------+
| 2019-07-03 21:01:20 | 25.827794561933533 |
+---------------------+--------------------+

mysql> SELECT datetime, AVG(distinct cost_time) FROM log_statis group by datetime;
+---------------------+---------------------------+
| datetime            | avg(DISTINCT `cost_time`) |
+---------------------+---------------------------+
| 2019-07-04 02:23:24 |        20.666666666666668 |
+---------------------+---------------------------+

keyword

AVG