AVG([DISTINCT] expr)
Used to return the average value of the selected field
Optional field DISTINCT parameters can be used to return the weighted average
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 | +---------------------+---------------------------+
AVG