Is uniqueness based on a single field or a combination of fields for a record to be considered "unique"?

>>As part of my thesis at Navy Postgraduate School, I have a genetic algorithm that runs in MS VFP 5.0. The output of the GA is a table with approximately 15 fields and usually about 5000 unique records. Every time I run the GA, I save the output in a table archive. Now, I have approximately 20 tables in the archive.
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>>I would like to create a new table which retrieves only the unique records from each of these 20 archived tables. There are no repeat records within each table. Again, each table has the same structure. I have tried appending records, which works, but it does not eliminate repeats. Is there a way of automatically eliminating repeats after the appendage? Or is there a method of using the 'join' (or some other) feature to do this? For each table, there is approximately 20%-30% intersection, so doing it manually is out of the question.
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>>Thank you,
>>LT Jason W. Carter
>>U.S. Navy
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>Jason, How about this... If the records which you do not want repeated are exact duplicates append all of them into one file, then use an SQL-Select something like this to get your unique records. "Select distinct * from appended_table into table new_table"