SQL to calculate daily average for a column with records of some dates are missing - sql

Question

I have table like below:
I have to calculate daily average count of session for each user.
First i calculated, total no of sessions for each day for every user and from that i tried to calculate average of daily session. I understand that it wont work since all users dont have sessions for every date.Some dates are missing for all users. Is there any way to calculate daily average when there is no entries for some dates
WITH daily_count AS
(
SELECT user_id, to_char(local_time,’MM/DD/YYYY’) AS Date, count(session_id) AS total_count
FROM table_name
GROUP BY device_id, to_char(local_time,’MM/DD/YYYY’)
)
SELECT user_id , AVG(total_count) AS average_session_count
FROM daily_count
GROUP BY user_id
For eg: The max date in the above given table is Feb04 and the min date is Jan31 .So the total no of days is 5 days.If we take Userid 1, it is having records only for 2 dates. So the query i wrote will calculate average for 2 days not for 5 days. How to make it to calculate average for 5 days

Answer 1

if for date 1,2,3 number of sessions for one user is 1,0(no sessions),5 then what output do you want in average sessions? --> 2 or 3?
You need to change your main query as follows:
SELECT USER_ID,
AVG(TOTAL_COUNT) AS AVERAGE_SESSION_COUNT -- if you want output as 3 then use this
--SUM(TOTAL_COUNT)/(MAX(DATE) - MIN(DATE) + 1) -- if you want output as 2 then use this
FROM DAILY_COUNT
GROUP BY USER_ID