Query Tuning

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Query Tuning

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Paul White SSC Guru Points: 150467 More actions · Answer 1

Sergiy (1/12/2012)
Explanation:
Nothing is stopping an INDEX SEEK from being used and answer "A" is the correct answer.
Actually something does.
It's named "bookmark lookup".

There is no 'bookmark lookup' in this case as Jeff's explanation of point H reveals: the non-clustered index is covering for the query.

'Bookmark lookup' is out-of-date now: they are referred to as an RID Lookup for a heap, or Key Lookup for a clustered index. The lookup operation is a seek on the clustered index key, or direct navigation to a row locator (RID) if the base table is a heap.

Paul White
SQLPerformance.com
SQLkiwi blog
@SQL_Kiwi

Sergiy SSC Guru Points: 110206 More actions · Answer 2

SQL Kiwi (1/12/2012)
There is no 'bookmark lookup' in this case as Jeff's explanation of point H reveals: the non-clustered index is covering for the query.

Sounds right.

I need to find out what did I do wrong to make it do scan instead of seek in my test case.

🙂

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Code for TallyGenerator

Koen Verbeeck SSC Guru Points: 259085 More actions · Answer 3

Great question, thanks.

Need an answer? No, you need a question
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seth delconte SSCertifiable Points: 6388 More actions · Answer 4

Thanks for the question. Even though I got it wrong, I learned a lot. 🙂

_________________________________
seth delconte
http://sqlkeys.com

pmadhavapeddi22 SSCertifiable Points: 5306 More actions · Answer 5

I thought answer B is including answer A also, that is why i did not check answer A.

and i did a big mistake by not reading "select 2"

learned a lot through the explanation given by all. thanks every one 🙂