Question

In a tutorial I saw this SQL query:

SELECT a.id as a_id, a.info as a_info, 
       b.id as b_id, b.info as b_info 
FROM stats AS a 
JOIN stats as b
ON a.id != b.id 
LIMIT 25

The query is working well, but now I would need to add the WHERE condition. I have the table users. The table stats contains the column user_id.
I try to obtain all users from the table stats if users.city=1 (for example), but I still cannot to find a way, how to achieve that…

My problem is, that I currently have no clue, how to put into the query another JOIN (for table users).

I would be grateful for every advice, thank you

Answer 1

Well, as you use the table stats two times in your query, you would actually need two joins for the users table as well. (for stats A and stats B)

SELECT a.id as a_id, a.info as a_info, 
       b.id as b_id, b.info as b_info 
FROM stats AS a 
JOIN stats AS b ON a.id != b.id 
JOIN users AS a_users ON a.user_id = a_users.id
JOIN users AS b_users ON b.user_id = b_users.id
WHERE a_users.city = 1 
   OR b_users.city = 1
LIMIT 25