Question

I have MySQL table that contains all messages from user to user:

id | to_id /*user_id*/ | from_id /*user_id*/
 1 |  32               |  54
 2 |  54               |  32
 3 |  32               |  54

The goal is get MySQL answer like list of dialogs user_id – user_id ordered by date. But if i do sql query:

select * from messages group by to_id, from_id

i will get

 to_id /*user_id*/ | from_id /*user_id*/
  32               |  54
  54               |  32

But first and second string is the same dialog. How can i group this records?

Answer 1

SELECT DISTINCT LEAST(from_id, to_id), GREATEST(from_id, to_id) FROM messages