>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.
>
>
>>It is in SQL Server starting from 2005 and up. I am not sure about other vendors such as Oracle or MySQL, someone who uses them may tell.
>>
>>>Do you happen to know in which SQL (as in 92,99,2003) this is defined and which vendors support it ?
>>>

As far as I can tell mysql does not support EXCEPT, but the left join approach works with mysql