Removing duplicates with unique index : <p>I inserted between two tables fields A,B,C,D, believing I had created a Unique Index on A,B,C,D to prevent duplicates. However I somehow simply made a normal index on those. So duplicates got inserted. It is 20 million record table.</p>

<p>If I change my existing index from normal to unique or simply a add a new unique index for A,B,C,D will the duplicates be removed or will adding fail since unique records exist? I'd test it yet it is 30 mil records and I neither wish to mess the table up or duplicate it.</p>
