Finding duplicate values using a self-join relationshipThis procedure uses a self-join relationship and a calculation field referencing the relationship to determine when duplicate records exist.
2. Identify a field that determines a unique entity in your file.For example, in a Contacts database, the Last Name field is probably not a good choice, because you might have several people with the same last name. Employee ID is a better choice. You can also create a calculation field (returning a text result) that combines data in several fields to make a unique identifier. An example formula is First Name & Last Name & Phone Number.Use your chosen identifying field as the match field in both tables in the relationship. See Creating relationships.
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6. Perform a find for Duplicates in the Check Duplicates field.All records with duplicates are marked Duplicates.