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Index Types


Index Types

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WayneS
WayneS
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Comments posted to this topic are about the item Index Types

Wayne
Microsoft Certified Master: SQL Server 2008
Author - SQL Server T-SQL Recipes
If you can't explain to another person how the code that you're copying from the internet works, then DON'T USE IT on a production system! After all, you will be the one supporting it!
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bitbucket-25253
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Very nice question ... thanks Wayne

If everything seems to be going well, you have obviously overlooked something.

Ron

Please help us, help you -before posting a question please read

Before posting a performance problem please read
Duncan Pryde
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Thanks for the question. I'd not come across filtered indexes before, so it's only 7:30am and I've already learnt something new today. Can't ask for much more than that!

Duncan
michael.kaufmann
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Wayne,

first of all thank you for compiling a QotD.
However, I do not quite agree with the solution.

'Unique' is just taking the definition of a clusterd or non-clustered index a step further.
'with included columns' and 'filtered' again are non-clustered indexes (with advanced features).
So I don't see them as individual types, but sub-types at best.

Hence it comes down to 5 types (why I got it wrong):
- clustered
- non-clustered
- full-text
- spatial
- XML

I assume, though, that this is another wording issue ;-); nevertheless an excellent lesson having to recap what index types there are.

Thanks,
Michael
hrvoje.piasevoli
hrvoje.piasevoli
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Would missing and unused make it 10?Smile

Hrvoje Piasevoli
cengland0
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michael.kaufmann (7/22/2010)
Wayne,

first of all thank you for compiling a QotD.
However, I do not quite agree with the solution.

'Unique' is just taking the definition of a clusterd or non-clustered index a step further.
'with included columns' and 'filtered' again are non-clustered indexes (with advanced features).
So I don't see them as individual types, but sub-types at best.

Hence it comes down to 5 types (why I got it wrong):
- clustered
- non-clustered
- full-text
- spatial
- XML

I assume, though, that this is another wording issue ;-); nevertheless an excellent lesson having to recap what index types there are.

Thanks,
Michael


I selected 5 as well and got it wrong. This question came up on another QOTD and there were disagreements on that one too.

The "Unique" index one is still a clustered or non-clustered type so it shouldn't be counted twice.

The "Index with included columns" is a non-clustered type.

The "Filtered" is a non-clustered type.

Taking the 8 listed, minus the 3 duplicates leaves 5.

If you want to argue this further, what about adding indexed views? What about Fragmented indexes (Not good but they do exist on tables updated frequently).
WayneS
WayneS
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hrvoje.piasevoli (7/22/2010)
Would missing and unused make it 10?Smile

Thanks for the early morning chuckle! Yes, you are right about this. :-D

Wayne
Microsoft Certified Master: SQL Server 2008
Author - SQL Server T-SQL Recipes
If you can't explain to another person how the code that you're copying from the internet works, then DON'T USE IT on a production system! After all, you will be the one supporting it!
Links: For better assistance in answering your questions, How to ask a question, Performance Problems, Common date/time routines,
CROSS-TABS and PIVOT tables Part 1 & Part 2, Using APPLY Part 1 & Part 2, Splitting Delimited Strings

WayneS
WayneS
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I would agree that Unique, filtered and included indexes are a sub-type of the clustered (for Unique) or non-clustered index types. However, according to the latest Microsoft documentation, they are a type of index. I'm not going to base a QotD off of what I believe it should be without any documentation to back me up.

You might want to take a look at SQL 2008 (R1) BOL for index types at http://msdn.microsoft.com/en-us/library/ms175049.aspx%28sql.100%29 - here they list 9 (they included Indexed Views). Since an Indexed View is a type of a view, physically manifested by having a clustered index and optionally having non-clustered indexes, I believe that it is correct that it was removed from this list.

Wayne
Microsoft Certified Master: SQL Server 2008
Author - SQL Server T-SQL Recipes
If you can't explain to another person how the code that you're copying from the internet works, then DON'T USE IT on a production system! After all, you will be the one supporting it!
Links: For better assistance in answering your questions, How to ask a question, Performance Problems, Common date/time routines,
CROSS-TABS and PIVOT tables Part 1 & Part 2, Using APPLY Part 1 & Part 2, Splitting Delimited Strings

george sibbald
george sibbald
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just to get my point back I would have to agree some of the index types MS list are really properties of an index, but hey-ho, I guess you can say a unique index is 'different' to a non-unique one.

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cengland0
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WayneS (7/22/2010)
I would agree that Unique, filtered and included indexes are a sub-type of the clustered (for Unique) or non-clustered index types. However, according to the latest Microsoft documentation, they are a type of index. I'm not going to base a QotD off of what I believe it should be without any documentation to back me up.

You might want to take a look at SQL 2008 (R1) BOL for index types at http://msdn.microsoft.com/en-us/library/ms175049.aspx%28sql.100%29 - here they list 9 (they included Indexed Views). Since an Indexed View is a type of a view, physically manifested by having a clustered index and optionally having non-clustered indexes, I believe that it is correct that it was removed from this list.


I don't subscribe to the logic that if it's on BOL, it must be true. If you want to include sub index types, you could include Ascending and Descending. The list could go on and on.
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