How do I loop through a table until condition reached - sql-server-2005

Question

I have a table product, pick_qty, shortfall, location, loc_qty
Product Picked Qty Shortfall Location Location Qty
1742 4 58 1 15
1742 4 58 2 20
1742 4 58 3 15
1742 4 58 4 20
1742 4 58 5 20
1742 4 58 6 20
1742 4 58 7 15
1742 4 58 8 15
1742 4 58 9 15
1742 4 58 10 20
I want a report to loop around and show the number of locations and the quantity I need to drop to fulfil the shortfall for replenishment. So the report would look like this.
Product Picked Qty Shortfall Location Location Qty
1742 4 58 1 15
1742 4 58 2 20
1742 4 58 3 15
1742 4 58 4 20

Answer 1

Note that it is best not to think about SQL "looping through a table" and instead to think about it as operating on some subset of the rows in a table.
What it sounds like you need to do is create a running total that tells how many of the item you would have if you were to take all of them from a location and all of the locations that came before the current location and then check to see if that would give you enough of the item to fulfill the shortfall.
Based on your example data, the following query would work, though if Locations aren't actually numerics then you would need to add a row number column and tweak the query a bit to use the row number instead of the Location Number; It would still be very similar to the query below.
SELECT
Totals.Product, Totals.PickedQty, Totals.ShortFall, Totals.Location, Totals.LocationQty
FROM (
SELECT
TheTable.Product, TheTable.PickedQty, TheTable.ShortFall,
TheTable.Location, TheTable.LocationQty, SUM(ForRunningTotal.LocationQty) AS RunningTotal
FROM TheTable
JOIN TheTable ForRunningTotal ON TheTable.Product = ForRunningTotal.Product
AND TheTable.Location >= ForRunningTotal.Location
GROUP BY TheTable.Product, TheTable.PickedQty, TheTable.ShortFall, TheTable.Location, TheTable.LocationQty
) Totals
-- Note you could also change the join above so the running total is actually the count of only the rows above,
-- not including the current row; Then the WHERE clause below could be "Totals.RunningTotal < Totals.ShortFall".
-- I liked RunningTotal as the sum of this row and all prior, it seems more appropriate to me.
WHERE Totals.RunningTotal - Totals.LocationQty <= Totals.ShortFall
AND Totals.LocationQty > 0
Also - as long as you are reading my answer, an unrelated side-note: Based on the data you showed above, your database schema isn't normalized as far as it could be. It seems like the Picked Quantity and the ShortFall actually depend only on the Product, so that would be a table of its own, and then the Location Quantity depends on the Product and Location, so that would be a table of its own. I'm pointing it out because if your data contained different Picked Quantities/ShortFall for a single product, then the above query would break; This situation would be impossible with the normalized tables I mentioned.