Question

I have a table:

ID int
category int
quantity int
timestamp timestamp

I want to SELECT id=”id#” and return a ‘position’ which is the sum of quantity for each row that has an earlier timestamp in the same category.

Thanks for your pointers!

Answer 1

Try this:

SELECT sum(quantity) FROM TABLE WHERE category='...' AND timestamp < some_timestamp

If you want to select by id:

SELECT sum(quantity) FROM mytable
WHERE category IN (SELECT category FROM mytable WHERE id=some_id)
AND timestamp <= some_timestamp

UPDATE

To use the timestamp from the row itself, you could do something like:

SELECT sum(quantity) FROM mytable
WHERE category IN (SELECT category FROM mytable WHERE id=some_id)
AND timestamp <= (SELECT timestamp FROM mytable WHERE id=some_id)

..or use a self-join as in the Adam’s answer (maybe it wasn’t an overkill, after all.. :))

UPDATE – Alternate solution

This seems to work fine too..

SELECT t1.id, sum(t2.quantity), t1.timestamp, t1.category
FROM mytable t1 INNER JOIN mytable AS t2 ON t1.category=t2.category
WHERE t1.id=some_id_here AND t2.timestamp <= t1.timestamp;

UPDATE

Changed < into <=, else the quantity for the selected item will not be counted!