Table Access Order

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Table Access Order

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Ken SSCoach Points: 17191 More actions · Answer 1

Ken

SSCoach

Points: 17191

September 20, 2011 at 7:56 am

#1383858

Nice question, thanks!

chrisfradenburg SSCrazy Eights Points: 9592 More actions · Answer 2

It's been good getting some of these harder questions that require knowing how SQL works. Thanks for taking the time to put them together.

Toreador SSChampion Points: 11365 More actions · Answer 3

I was expecting to see "undetermined, could be either" as an option so guessed (wrongly as usual).

Learned something new - not sure how useful it is to know, but these things are always interesting 🙂

Trey Staker SSCarpal Tunnel Points: 4796 More actions · Answer 4

Got it wrong 🙁

Thanks for the question, eventhough I got it wrong I learned something. Great explanation!

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Paul White SSC Guru Points: 150467 More actions · Answer 5

Toreador (9/20/2011)
Learned something new - not sure how useful it is to know, but these things are always interesting 🙂

It depends. The average DBA can get by perfectly well with just a basic understanding of execution plans.

But who wants to be average?

Paul White
SQLPerformance.com
SQLkiwi blog
@SQL_Kiwi

OzYbOi d(-_-)b SSCarpal Tunnel Points: 4054 More actions · Answer 6

OzYbOi d(-_-)b

SSCarpal Tunnel

Points: 4054

September 20, 2011 at 10:53 am

#1384010

great question

Ninja's_RGR'us SSC Guru Points: 294069 More actions · Answer 7

SQL Kiwi (9/20/2011)
Toreador (9/20/2011)
Learned something new - not sure how useful it is to know, but these things are always interesting 🙂
It depends. The average DBA can get by perfectly well with just a basic understanding of execution plans.
But who wants to be average?

Who works hard enough to be exceptional?

Enough said :hehe:.

CoolCodeShare SSCrazy Points: 2584 More actions · Answer 8

CoolCodeShare

SSCrazy

Points: 2584

September 20, 2011 at 10:22 pm

#1384309

Nice question and learnt something!

Koen Verbeeck SSC Guru Points: 259105 More actions · Answer 9

Excellent question, thanks!

Need an answer? No, you need a question
My blog at https://sqlkover.com.
MCSE Business Intelligence - Microsoft Data Platform MVP

Toreador SSChampion Points: 11365 More actions · Answer 10

SQL Kiwi (9/20/2011)

But who wants to be average?

I dream of being average, but have quite a way to go still to achieve it 🙂

Mattrick Ten Centuries Points: 1176 More actions · Answer 11

Great question, Paul. It is always a good thing to know what is going on under the hood.

Thanks,

Matt

Andre Guerreiro SSCertifiable Points: 7319 More actions · Answer 12

Thank you for such an amazing question, Paul.

I got it right because I always remember reading that the "top (outer) input" is read first and then it goes look for matches in the "bottom (inner) input". Even the Nest Loops operator works this way, right?

I just started reading the excellent Execution Plan book from Grant Fritchey.

It was a nice timing for me. 🙂

Best regards,

Andre Guerreiro Neto

Database Analyst
http://www.softplan.com.br
MCITPx1/MCTSx2/MCSE/MCSA

Paul White SSC Guru Points: 150467 More actions · Answer 13

codebyo (9/22/2011)
I got it right because I always remember reading that the "top (outer) input" is read first and then it goes look for matches in the "bottom (inner) input". Even the Nest Loops operator works this way, right?

Right. 🙂

http://sqlblog.com/blogs/paul_white/archive/2010/08/05/iterators-query-plans-and-why-they-run-backwards.aspx

Paul White
SQLPerformance.com
SQLkiwi blog
@SQL_Kiwi

Andre Guerreiro SSCertifiable Points: 7319 More actions · Answer 14

SQL Kiwi (9/23/2011)
http://sqlblog.com/blogs/paul_white/archive/2010/08/05/iterators-query-plans-and-why-they-run-backwards.aspx

I have been following your blog for some time now but I hadn't found that article before. I have much to learn and I appreciate those links.

Can I print that article for my personal use and to show it to my workmates?

I'm trying to help them understand the basics of the execution plans and they get confused about the order of what's happening and why. I'm performing basic training about this subject to help them improve their queries which are very slow.

Today I was confronted with an old code that joined 20 tables and then had a cursor to manage that. We successfully replace that code and improved what was once running in almost 10 minutes to 50 seconds. It still isn't optimized enough but we'll soon get there.

Thank you for the amazing articles you post.

Best regards,

Andre Guerreiro Neto

Database Analyst
http://www.softplan.com.br
MCITPx1/MCTSx2/MCSE/MCSA

Paul White SSC Guru Points: 150467 More actions · Answer 15

codebyo (9/23/2011)
SQL Kiwi (9/23/2011)
http://sqlblog.com/blogs/paul_white/archive/2010/08/05/iterators-query-plans-and-why-they-run-backwards.aspx
I have been following your blog for some time now but I hadn't found that article before. I have much to learn and I appreciate those links. Can I print that article for my personal use and to show it to my workmates?

Well thanks, I wondered who the other reader was 🙂

Of course you may print it and show it around, I only object when people copy my work and attempt to pass it off as their own (sadly this does happen).

Adam (Machanic) would no doubt want me to encourage you to share a link to SQLblog instead (traffic = advertising = pays the hosting bills) but I understand that is not always possible.

Paul White
SQLPerformance.com
SQLkiwi blog
@SQL_Kiwi