MySQL Select Distinct Count

Question

+----------+----------+ | user_id  | video_id | +----------+----------+ |        1 |    1     | |        1 |    1     | |        1 |    2     | |        2 |    1     | |        2 |    2     | +----------+----------+ 

I have a table setup similar to the one above. I would like to return a total count from my query.

For each user_id they need to have a DISTINCT video_id. So above, user_id = 1 would have 2 unique video_id's and user_id = 2 would have 2 unique video_id's. This would make the total 4. I'm not sure the best way to organize my query to achieve the desired result.

Basically for each user_id, I need something like, COUNT(DISTINCT video_id)

I would like the final result just to return total count of everything.

Answer 1

If you want to get the total count for each user, then you will use:

select user_id, count(distinct video_id) from data group by user_id; 

Then if you want to get the total video_ids then you will wrap this inside of a subquery:

select sum(cnt) TotalVideos from (   select user_id, count(distinct video_id) cnt   from data   group by user_id ) d 

See SQL Fiddle with Demo of both.

The first query will give you the result of 2 for each user_id and then to get the total of all distinct video_ids you sum the count.