MySQL Select Distinct Count

Question

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.