Question

I have a table for friends

PLAYER_ID    FRIEND_ID
----------------------
1            2
1            3         // 1 knows 3
3            1         // 3 knows 1
2            4

How can I create a view containing those acquaintances(know each other) for given player?

PLAYER_ID    FRIEND_ID
----------------------
1            3
3            1

thank you.

Answer 1

Here’s the needed select:

select t1.PLAYER_id, t1.FRIEND_ID from tablename t1
inner join tablename t2 on t1.PLAYER_id = t2.FRIEND_ID and t2.PLAYER_id = t1.FRIEND_ID