Both. Create a self-relationship for the Holdings table, on the Firm ID and Ticker. Name the second instance 'Holdings Self'. Create a calculated field in Holdings, using the Count function. Select either the Firm ID or Ticker fields from Holdings Self to count. Anywhere this number is greater than 1, you have a duplicate.
Question: Is 2010 Q1 a field? Are there others like it? I.e. 2009 Q4, 2009 Q3, etc? If so, this is not very expandable. It would be better to have Year and Quarter fields in the table.
I think that did it, thank you! I've got to tweak my delete script a bit to make it more flexible, but it's definitely finding the duplicates OK!
And yes, 2010 Q1 is a field and there are other others like it as you suggest. How can I improve this/make it more expandable? We track holdings by quarter.