Searching for Duplicates

[dankitchen]

I am looking to search for duplicates in a column.  For example, I have a contacts search type with an email column.   I want to find all of the subjects where the email is duplicated.  I could do this by looping through each item and running a query but I feel like that might be heavy on the server so wondering if there is a simpler approach?

Thanks!
Dan

[listy]

If you doing so just to remove duplicates, then why bother about server load or anything else.