Eirikur Eiriksson - Saturday, May 26, 2018 1:35 AM
To add to that, you MUST include the target of the update in the FROM clause for joined updates like Eirikur did or you could end up with an update that will usually seem to work just fine and then someday... WHAM! A 6 second update will suddenly drive several CPUs to the stops and take hours to execute or fail due to a "halloweening-like" actual execution plan that won't show up as being so in an estimated execution plan even if the update doesn't cause the data movement that typical of the true "Halloweening" problem in databases.
Also, not having the target of the update in the FROM clause for joined updates is actually an illegal and certainly not supported form of UPDATE. You won't find any joined UPDATE example that doesn't have the target of the update in the FROM clause anywhere in Books Online or other Microsoft generated documentation.,
--Jeff Moden
Change is inevitable... Change for the better is not.