Question

I ran into a problem and was trying to find a general solution to it as a join.

I have 2 tables :

http://pastebin.com/q5yws5Ym (not sure how to enforce the styling)

And i want to generate something like
http://pastebin.com/GscBUrYS

(while there are more parameters i’m interested in how i would do it for something like this)

While i was able to reach a similar effect with self-joins and equi-joins it would generate a lot of unneeded rows, which i’m not sure how to delete automatically.

Answer 1

Try something along the lines of:

SELECT user.user_id, j1.user_param, j1.user_value, j2.user_param, j2.user_value
FROM user
JOIN Users_info j1 ON user.user_id = j1.user_id
JOIN users_info j2 on user.user_id = j2.user_id
where j1.user_param != j2.user_param
GROUP BY user.user_id

It may be possible that you will need some more “exclusion” clauses for the where to make sure that every row is only selected once but the general idea should work (for a given and limited number of different user_param`s).