2011/1/10 Mladen Gogala <mladen.gogala@vmsinfo.com>:
> Well, I really hoped that Bruce, Robert or Greg would take on this one, but
> since there are no more qualified takers, I'll take a shot at this one. For
> the "NOT IN (result of a correlated sub-query)", the sub-query needs to be
> executed for every row matching the conditions on the driving table, while
> the !EXISTS is just a complement of join. It's all in the basic set theory
> which serves as a model for the relational databases.
As Scott says, the real problem is the NULL handling. The semantics
are otherwise similar.
--
Robert Haas
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