Question

I need to identify missing products who’s numbers are sequential. In other words, there’s a set of products that are sold each with a unique number at each of our stores. The end user wants a report that will identify the missing widgets in a date range.

Store   Product Number
Store 1  Widget   100
Store 1  Widget   101
Store 1  Widget   102
Store 1  Widget   104
Store 2  Widget   201
Store 2  Widget   202
Store 2  Widget   203

I thought the best way to do this is to obtain the MAX(Number) and the MIN(Number) and then populate a table variable with all of the numbers in the sequence. If the Widget Number from the table variable doesn’t exist in the Product table, I would return the number and mark it as missing.

However; our DBA is very much against Cursors and I know WHILE loops take a lot of overhead. Plus, I’m not sure how to do this on a by store basis.

Does anyone know of the way to do this in a set based manner?

The widgets themselves have numbers, so when you sell widget #1, the next widget you sell should be widget #2. However; sometimes, that doesn’t happen and widget #3 is sold – widget #2 is missing and not in the database. I need to identify on a report that widgets #1 and #3 were sold and #2 is missing.

Answer 1

Updated Answer

Sample code to create a table and working solution are below. Basically you do 2 EXISTS checks – to see if there are numbers higher than the current number, and there is not a number one higher than the current number.

DECLARE @t Table (Store int, Product varchar(100), number int)
INSERT INTO @t
VALUES
(1, 'Widget',   100),
(1, 'Widget',   101),
(1, 'Widget',   102),
(1, 'Widget',   104),
(2, 'Widget',   201),
(2, 'Widget',   202),
(2, 'Widget',   203)

SELECT Store, Product, t.Number+1 as Missing
FROM @t t
WHERE EXISTS (SELECT 1 FROM @t t2
              WHERE t2.Store = t.Store
              AND t2.product = t.product
              AND t2.number > t.number)
AND Not Exists (SELECT 1 FROM @t t3
                WHERE t3.Store = t.store
                AND t3.product = t.product
                AND t3.number = t.number + 1)