I tested it on your sample data and it works correctly.
Can you post your query?

>Sorry but it does not work at all... I got something like this...

>Sku            Store  WeekNo
>-------        -----  -------
>1000419	003	39
>1000419	004	20
>1000419	004	24
>1000419	006	40
>1000419	008	10
>1000419	008	18
>1000419	009	20
>1000419	009	39
>1000419	009	52