Import into List - duplicates in key
I want to import a customer forecast into a module.
The customer forecast is
Key, Product, Location, Date, Qty
My end module will have a key dimension which is the Product/Location and dimension time,
with a value of qty.
So part of the import process is to create the key List.
If I import into the key list from the customer forecast file I get duplicates for product/location key for every time period that exists.
I could get round this by creating a key that includes time and create a very big list, and then importing from this into another shorter key list excluding time. But this seems to be creating what should be unnecessary lists/data
Ideally I would like the duplicates when importing into my keys list to not be an error.
Is there any way round this without having to create long lists to then shorten them?