Insert without duplicates mysql without unique key
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I have a program that is reading a credit card statement and I need it to insert it into a table. The problem i am having is when i just use insert it will let the user insert the same information over and over again. However I really cant set any of the columns as unique because there can be duplicates in all of the fields.
The fields i have are DATE | Description | Amount    
So the user could have used the card on the same date at the same place and for the same amount. These are monthly statements so is there a way to do this besides insert ignore while using a unique key??
Brent