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Statement evaluation precedence


Statement evaluation precedence

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Tom Brown
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Comments posted to this topic are about the item Statement evaluation precedence
Oleg Netchaev
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This is a very good question, thank you Tom. Today I am the lucky one to be first who answered it correctly. It was not too difficult to deduce correct answer because it was the only one noticeably making perfect sense. The Logical Query Processing Diagram is great, I will definitely print it out and have it posted on the wall by my desk.

Oleg
Paul White
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Yay! Another point. Found this one quite easy - but only because I happened to re-read Itzik Ben-Gan's Inside Microsoft SQL Server 2008: T-SQL Querying recently. (Chapter 1)

Itzik describes the logical order of processing as:

FROM
Cartesian Product
ON clause filter
Add Outer Rows
WHERE
GROUP BY
HAVING
SELECT
Evaluate expressions
DISTINCT
TOP
Presentation ORDER BY

I would just add that the physical order of operations performed may differ from the logical order due to query optimisation.

Well done Tom.

edit: added further details after re-reading the question explanation



Paul White
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woot - got it correct.



Jason AKA CirqueDeSQLeil
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Though I got this correct, it appears there is a typo in the correct answer. My version had the last two flip-flopped based on the source document provided in the answer.



Jason AKA CirqueDeSQLeil
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Paul White
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CirquedeSQLeil (5/6/2010)
Though I got this correct, it appears there is a typo in the correct answer. My version had the last two flip-flopped based on the source document provided in the answer.

What are you referring to here Jason?
It must be hard to spot - I can't see anything wrong...Unsure



Paul White
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sharath.chalamgari
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Good Question Tom:-)
Tom Brown
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Thank-you all.

I've had this data for 10 years now, maybe I copied it from someone's SQL 2000 book - or possibly it came from an SQL 7 course I did (in 1999!), and I found it really useful, But I was slightly unsure that it was still valid, particularly as I had some difficulty in finding a concrete reference.


Thanks Paul for the tip on Itzik's book - I'll be visiting Amazon soon I think (or should I wait for the R2 edition?)
ziangij
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got to learn something new today... thanks :-)
Stewart "Arturius" Campbell
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Had to wrack the grey matter on this one - haven't thought about it for several years...
good question.

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