mysql - Return rows in common with another user in SQL (Collaborative Filtering) -

i'm trying build basic collaborative filtering recommendation system using mysql. have user rating table this:

    user_id movie_id rating 1   131     342      3      <<< user 131 has rated movie 342  2   131     312      5      <<< , 312 3   122     312      4   4   213     342      5 5   141     342      5      <<< user 141 has rated 342 6   141     312      4      <<< , 312 (2 movies in common)  7   141     323      3 

so i'm trying find similar users 131. want return users have @ least 2 movies in common , ratings above 3. should return rows 5 , 6 (as shown above).

this have far:

select * user_ratings rating >= 3 , movie_id in (select movie_id user_rating user_id = 131) , user_id != 131  

this returns:

    user_id movie_id rating 3   122     312      4     <<< don't want these 2 4   213     342      5     <<< 5   141     342      5      6   141     312      4       

it returns movies users have in common 131, need show users have @ least 2 items in common. how this? i'm unsure of how proceed :(

you can first find user_ids have more or equal number of movies user_id = 131 rating > 3. use in in where clause additional data:

sql fiddle

select * user_ratings     user_id in(         select user_id         user_ratings                      movie_id in (select movie_id user_ratings user_id = 131)             , rating > 3         group user_id         having             count(*) >= (select count(*) user_ratings user_id = 131)     )     , rating > 3