August 30, 2017 at 11:57 pm
Comments posted to this topic are about the item The Order of Processing
August 30, 2017 at 11:58 pm
Back to basics, thanks Steve
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August 31, 2017 at 7:14 am
Good to see 90% got it right so far.
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This thing is addressing problems that dont exist. Its solution-ism at its worst. We are dumbing down machines that are inherently superior. - Gilfoyle
August 31, 2017 at 8:46 am
A good refresher, Thanks Steve
August 31, 2017 at 9:33 am
August 31, 2017 at 10:05 am
My thoughts exactly (I came here to see if anyone had commented yet). My assumption is that the ON is deciding what to join and how, and then the JOIN applies LEFT/RIGHT/INNER/OUTER/CROSS.
August 31, 2017 at 2:19 pm
September 1, 2017 at 2:53 am
Thanks Steve, an interesting article, but it does rather contradict the order given in your answer. You have FROM, ON, JOIN..., but in figure 4 in Ben-Gan's article it has JOIN->ON (or rather it just has JOIN, with ON as the second step in the JOIN).
September 1, 2017 at 5:32 am
Nice, simple question, thanks Steve
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September 1, 2017 at 9:48 am
Andrew Watson-478275 - Friday, September 1, 2017 2:52 AMThanks Steve, an interesting article, but it does rather contradict the order given in your answer. You have FROM, ON, JOIN..., but in figure 4 in Ben-Gan's article it has JOIN->ON (or rather it just has JOIN, with ON as the second step in the JOIN).
I think the ON is processed first, to determine how to apply the join based on indexes. Itzik has grouped them, while MS has separated them. In his book, he listed ON as coming before JOIN, but in revisions he's combined them in a step, perhaps because JOIN v ON doesn't practically matter? Not sure.
September 5, 2017 at 3:03 pm
Steve Jones - SSC Editor - Friday, September 1, 2017 9:48 AMAndrew Watson-478275 - Friday, September 1, 2017 2:52 AMThanks Steve, an interesting article, but it does rather contradict the order given in your answer. You have FROM, ON, JOIN..., but in figure 4 in Ben-Gan's article it has JOIN->ON (or rather it just has JOIN, with ON as the second step in the JOIN).I think the ON is processed first, to determine how to apply the join based on indexes. Itzik has grouped them, while MS has separated them. In his book, he listed ON as coming before JOIN, but in revisions he's combined them in a step, perhaps because JOIN v ON doesn't practically matter? Not sure.
I believe that before you do anything, you have to find what data you are working with, so for me it was a no-brainer. Thanks, Steve!
September 5, 2017 at 6:11 pm
It's a very important point in understanding how SQL works as a declarative language. Down to 84% correct, but still a good percentage.
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