Paul White (11/7/2009)
The EXISTS does not need a Stream Aggregate (present in both of your examples) and uses a left semi join instead of a left outer join. The obvious difference there is that the semi join stops processing as soon as it finds a match; the left outer join processes all matches.
Thanks for your explanation!
I know, the joined UPDATE is slightly less performing in this case. The main reason why I'm using it is, I've seen several inline sub-queries which ended up in a row based execution. Since I don't know the SQL Server internals like you do, the joined syntax is more secure for newbies like me :-P.
Greets
Flo