>>There are other ways to do this. Getting duplicate key values from a table is a simple SQL SELECT statement, and another statement afterwards can be used to delete all but one...
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>What statement do you use to delete all but one?

If you get a list of unique records using GROUP BY in one table, and copy that table over the original. THere are other ways that take a few more steps...
Not necessarily better than using the unique index approach, I'm just pointin out that a unique index is not needed to do this.