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  3. April 2008

Re: SQL exception join: Left side now needs data combined from two tables

Dan wrote:
Elvis, it seems odd that UNION would, by default (DISTINCT), weed out
duplicates. Is that the SQL standard? In this case, I don't think it
affects this query, as all records between the two tables are unique.

I hope you don't mind if I chime in here. I'm not sure, but I'd guess it's the SQL standard.

My understanding is that the UNION is based on the mathematical set-theory concept of a union. By definition, sets don't contain duplicate elements.

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