Question

I have a table with items that are part of a thread, so they have a thread ID, each item also has a date (UNIX timestamp). My table looks something like the following (UNIX timestamps simplified):

+-----------------------------+
|  id |   date  |  thread_id  |
+-----+---------+-------------+
|  1  |   1111  |      4      |
|  2  |   1333  |      4      |
|  3  |   1444  |      5      |
|  4  |   1666  |      5      |
+-----------------------------+

What I want to do is select thread IDs where ALL the items sharing the same thread ID are smaller than the passed date. So if I wanted thread IDs where ALL items are older than 1555 (date < 1555), I would only expect to have thread ID 4 returned, not 5 even though it’s got an item with a date smaller than 1555. This is what I tried:

SELECT * FROM table WHERE date < 1555 GROUP BY thread_id ORDER BY date DESC

What I’m trying to do with that query is group all items by thread ID around the item with the highest date value and from there get the items where the date is less than 1555. But that doesn’t work, it will still return thread ID 5 because it’s got an item older than 1555.

So to summarize, how would I only select thread IDs where ALL items are older than a certain date?

Answer 1

SELECT thread_id FROM table GROUP BY thread_id HAVING MAX(date) < 1555