AVG

Description

Calculates the average of all non-NULL values in a specified column or expression.

Syntax

AVG([DISTINCT] <expr>)

Parameters

Parameter	Description
<expr>	It is an expression or column, typically a numeric column or an expression that can be converted to a numeric value.
[DISTINCT]	It is an optional keyword that indicates the calculation of the average value after removing duplicate values from expr.

Return Value

Returns the average value of the selected column or expression. If all records in the group are NULL, the function returns NULL.

Example

SELECT datetime, AVG(cost_time) FROM log_statis group by datetime;

+---------------------+--------------------+
| datetime            | avg(`cost_time`)   |
+---------------------+--------------------+
| 2019-07-03 21:01:20 | 25.827794561933533 |
+---------------------+--------------------+

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 |
+---------------------+---------------------------+