mysql - SQL select query about grouping 2 columns -

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i trying head around query - seems pretty straight forward

the table below captures user watched video

 topic_user_id | topic_id | user_id      1        |   10     |   3      2        |   10     |   4      3        |   11     |   5      4        |   11     |   3      5        |   12     |   6      6        |   13     |   6      7        |   14     |   7      8        |   11     |   8      9        |   11     |   9      10       |   14     |   10      11       |   15     |   11      12       |   16     |   11      13       |   17     |   11

now find out how many users watched particular video - have following query.

how many users have watched particular video

 select count(distinct(user_id)) 'number of users',topic_id topic_user user_id not null group topic_id

output

 number of users | topic_id      2           |   10          4           |   11          1           |   12          1           |   13          2           |   14          1           |   15          1           |   16          1           |   17       read as: 2 users watched topic 10 , 4 watched topic 11 , on

this works fine - looking find :

how many users watched 1 video
how many users watched 2 videos
how many users watched 3 videos

the output should like

 number of users  | number of videos watched       6          |       1       2          |       2       1          |       3  read - 6 people watched 1 video, 2 people watched 2 videos , on.

need this.

thanks in advance

there may easier way subquery work

select     videos 'number of videos',     count(user_id) 'num of users' (    select         count(distinct(topic_id)) videos,         user_id topic_user    group         user_id  ) sub  group     videos

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