Message table from where i want to get recent contacts for 'user1', now the table looks like this:
| id | receiver | sender | time |
|----|----------|--------|------------|
| 1 | user1 | host1 | 2020-07-02 |
| 2 | host2 | user1 | 2020-07-03 |
| 3 | user3 | host3 | 2020-07-04 |
I managed to get the expected result by using mysql:
SELECT CASE WHEN receiver = 'user1' THEN sender ELSE receiver END AS id, max(time) AS time
FROM message WHERE receiver = 'user1' OR sender = 'user1'
GROUP BY CASE WHEN receiver = 'user1' THEN sender ELSE receiver END;
But when i run this query on postgres i get the error: Postgresql error: column receiver must appear in the GROUP BY clause or be used in an aggregate function. Any solution to fix this problem?
I would suggest distinct on:
select distinct on ( case when receiver = 'user1' then sender else receiver end ) m.*
from messages m
where 'user1' in (receiver, sender)
order by (case when receiver = 'user1' then sender else receiver end), time desc;