Count one value based on another value...

[caman74]

Hello.

I do have, in my db, a single table.
I have the fields:
"ID"
"Productnumber"
"Location"
"In_Stock"
"Total_Locations"

My question is;
I have several productnumbers, both with and without letters/ numbers, but they are not unique.
Each Productnumber is given a location.
Each location is not unique to that productnumber.
But, I might have the same productnumber several times, but with different locations.

I need the field "Total_Locations" to count the number of unique locations, for each Productnumber.

I.E. I have:
PO# "920-580" on both Location "H1" and "291504".
The "Total_Locations" would be 2.

PO# "MayOS" is located only on Location "VM2".
The "Total_Locations" would be 1.

You get my drift?

Regards

Christian