>Do you happen to know in which SQL (as in 92,99,2003) this is defined and which vendors support it ?
>

I don't know when it came into the standard. But looks like it's in SQL Server 2005 and later. PostgreSQL supports it, though I don't know starting when. Don't know about any others.

Tamar

>>>Yes, the "null" method blew my mind when I first encountered it (in an example much more complex, using a join Select). Using it has trimmed 80% off the SQL times (against SQL Server 2014) in our large queries, compared to IN SELECT. SQL Server, for one, produces the same Query Plan for EXISTS and IN SELECT, in case anyone is wondering.
>>>
>>
>>In SQL Server, why wouldn't you use the EXCEPT keyword?
>>
>>

>>SELECT iID FROM Table2
>>EXCEPT
>>SELECT iID FROM Table1
>>

>>
>>http://www.tomorrowssolutionsllc.com/Articles/Combining%20Query%20Results.pdf
>>
>>Tamar