Question

I’m just stuck with a simple mysql query, I want to update the row having max Id of a table, and I was trying something like but it doesn’t work

UPDATE inbox i
INNER JOIN messages m ON i.message_id = m.id 
SET i.read = 0
WHERE m.conversation_id = 10
AND i.user_id = 1
ORDER BY i.id DESC
LIMIT 1

I’ve also tried sub query but it doesn’t work either

Need some help on it.

Thanks

Answer 1

In MySql you can’t update a table if you have a subquery that references the same table, but you could sostitute the subquery with JOINS. I would do this, it’s a trick but it works:

UPDATE
  inbox inner join (select max(id) as maxid from inbox) mx on inbox.id = mx.maxid
SET inbox.`read` = 0

EDIT: I see you edited your question, so i have to edit my answer:

UPDATE
  inbox
  INNER JOIN (select max(inbox.id) as maxid
              from
                inbox inner join messages
                on inbox.message_id = messages.id
              where
                messages.conversation_id=10
                and inbox.user_id=1) mx
  on inbox.id = mx.maxid
SET inbox.`read` = 0

Your subquery returns the maximum id based on the conversation_id and the user_id you want, then you join inbox whith the maximum id to select just the row you want, and you can then update just that row.