Question

I got 3 tables:

1. items (item_id, timestamp)
2. items_terms (item_id, term_id)
3. terms (term_id, term_name)

I need to find 5 most recent terms (term_id, term_name) based on item timestamp. I was trying to solve it like this:

SELECT t.term_id, t.term_name
 FROM items i
  INNER JOIN items_terms it USING(item_id)
  INNER JOIN terms t USING (term_id)
GROUP BY t.term_id 
ORDER BY i.timestamp DESC
LIMIT 5

But the problem is that MySQL will group items first (it will take the first term_id) and disregard ORDER BY..

I was also thinking about filtering on PHP side by removing GROUP BY and selecting more than 5 items, but this query needs to support pagination without duplicates on consecutive pages.

Will be glad to see any suggestions.

Answer 1

How about including the timestamp in the select statement:

SELECT t.term_id, t.term_name, MAX(i.timestamp)
 FROM items i
  INNER JOIN items_terms it USING(item_id)
  INNER JOIN terms t USING (term_id)
GROUP BY t.term_id, t.term_name
ORDER BY MAX(i.timestamp) DESC
LIMIT 5