Question

The following SELECT statement

select * 
from messages 
where receiverID = '5' 
group BY senderID 
order by id DESC

database:

id | senderID | receiverID | message
1  |  245     |    5       | test 1
2  |  89      |    5       | test 2
3  |  79      |    5       | test 3
4  |  245     |    5       | test 4
5  |  245     |    5       | test 5

For senderID=245 I expected to return the row with id=5 , but it dosent it returns row with id=1, but i want the last row. How to achieve that ?

returns:

id | senderID | receiverID | message
1  |  245     |    5       | test 1
2  |  89      |    5       | test 2
3  |  79      |    5       | test 3

---

Ohh I made it 😀

so this is the code that worked,for anyone with similar question

     SELECT * FROM ( SELECT * FROM messages WHERE
 receiverID = '5' ORDER BY id DESC) AS m GROUP BY senderID ORDER BY id DESC

Answer 1

Not sure I understand your question completely, but it sounds to me like you want:

select max(id), 
       senderId, 
       max(receiverId), 
       max(message)
from messages 
where receiverID = '5' 
group BY senderID 
order by id DESC

Note that you need to include message into your aggregate as well, otherwise you’ll get unpredicatable results (other DBMS wouldn’t allow leaving out the max(message) but MySQL will simply return a random row from the group).