Creating query for printing average of two months [closed]

I need to show monthly average of total using SQL and PHP. For example this table has total=254 in June & total=315 in July. I need to show their average i.e. (254+315)/2= 284.5

What SQL query should I make to print their average using PHP?

Answer

One method is:

select sum(total) / count(distinct extract(year_month from date))
from t;

This sums the total column and divides by the number of months. If you need this for the particular two months, then include a where clause:

select sum(total) / count(distinct extract(year_month from date))
from t
where date >= '2020-06-01' and date < '2020-08-01'

If you wanted to count missing months as 0 for the average purposes, then use a constant:

select sum(total) / 2
from t
where date >= '2020-06-01' and date < '2020-08-01'