Well, I spent a long time last night trying to apply a unique index to an Oracle table. It kept telling me that it couldn't apply it because I had duplicate records already in that table. I kept searching for the duplicates with the tried and true method of:
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SELECT proposal_no FROM proposals A where ROWID > (
SELECT min(ROWID) FROM proposals B
WHERE A.key_values = B.key_values) |
And wasn't finding them, no matter how much coke I drank. The answer, as some probably have already guessed is that Oracle will recognize NULL values as duplicates but not equal in terms of Null = Null so NULLS won't show up in a query like the above.
5:39:46 PM 
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