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    <p>Your approach is flawed. You do not want data that was successfully able to be stored to then throw an error on a select - that is a land mine waiting to happen and means you never know when a select could fail.</p> <p>What I recommend is that you add a unique key to the table, and slowly start modifying your application to use this key rather than relying on any combination of meaningful data.</p> <p>You can then stop caring about duplicate data, which is not really duplicate in the first place. It is entirely possible for two people with the same name to share the same address.</p> <p>You will also gain performance improvements from this approach. </p> <p>As an aside, I highly recommend you normalize your data, that is break up the name into FirstName and LastName (optionally MiddleName too), and break up the address field into separate fields for each component (Address1, Address2, City, State, Country, Zip, or whatever)</p> <p><strong>Update:</strong> If I understand your situation correctly (which I am not sure I do), you want to prevent duplicate combinations of name and address from ever occurring in the table (even though that is a possible occurrence in real life). This is best done by a unique constraint or index on these two fields to prevent the data from being inserted. That is, catch the error <strong>before</strong> you insert it. That will tell you the import file or your resulting app logic is bad and you can choose to take the appropriate measures then.</p> <p>I still maintain that throwing the error when you query is too late in the game to do anything about it.</p>
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    1. POSafely normalizing data via SQL query
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    1. CO+1 any serious data table should definitely have a primary key to uniquely identify every single data row - database design 101!
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      1. USmarc_s
    2. COYou both are absolutely correct. I was hoping the question would be answered without people questioning its design. ;) I hope my latest edit can help shed some light on the question.
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      1. USAdam Paynter
 

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