>Thx. But is it in one of the SQL standards definitions as well ? I am pretty certain Exists was in SQL99, probably already in SQL92.
>If Except generates faster execution plans AND is in one of the standards, I'd use it even if not all others support it (yet), as it is expressive.
>If it is not standard, my rule of thumb would point to !null, if the speed of not in () or not exists create a problem.
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http://stackoverflow.com/questions/5557991/minus-vs-except-difference-in-oracle-sql-server