Is each serial number in a separate record?
If so, Comment posted a "sum the reciprocal" method that counts each unique entry once:
- Define a summary field sTotalCount as Count Of: SerialNumberField
- Define a calculation field cFraction as 1 / GetSummary ( sTotalCount ; SerialNumberField )
- Define another summary field sUniqueCount as Total Of: cFraction
Sort your records by SerialNumberField and sUniqueCount will give you the correct number of unique values.
Here's a demo file of the concept: http://www.4shared.com/file/7SAsWs1M/SumTheReciprocal.html
I downloaded the SumTheReciprocal file to see how this works.. I would have thought "goats would have a '1', cows a '3' and so on to represent the unique count of each value. Even after sorting - I get '4's' in the sUniqueCount field.
Your assistance would be greatly appreciated. Thank you!