Question

I have a table of items by date (each row is a new date). I am drawing out a value from another column D. I need it to replace 0s though. I need the following logic: when D=0 for that date, use the value in column D from the date prior.

Actually, truth be told, I need it to say, when D is 0, use the value from the latest date where D was not a 0, but the first will get me most of the way there.

Is there a way to build this logic? Maybe a CTE?

Thank you very much.

PS I’m using SSMS 2008.

EDIT: I wasn’t very clear at first. The value I want to change is not the date. I want change the value in D with the latest non-zero value from D, based on date.

Answer 1

May be the following query might help you. It uses the OUTER APPLY to fetch the results. Screenshot #1 shows the sample data and query output against the sample data. This query can be written better but this is what I could come up with right now.

Hope that helps.

SELECT      ITM.Id
        ,   COALESCE(DAT.New_D, ITM.D) AS D
        ,   ITM.DateValue
FROM        dbo.Items   ITM
OUTER APPLY (
                SELECT      
                TOP 1       D   AS New_D
                FROM        dbo.Items DAT
                WHERE       DAT.DateValue   < ITM.DateValue
                AND         DAT.D           <> 0
                AND         ITM.D           = 0
                ORDER BY    DAT.DateValue DESC
            ) DAT

Screenshot #1: