A non-clustered index is just another way to get to data. Add in a couple columns and off you go. Not too much to think about, just fire and forget. But it’s not really that easy. Non-clustered indexes have a number of various ways in which they can be built and designed that can have significant impacts on performance. In this session we’ll look at what can go into a non-clustered index. We will explore what you can put into a non-clustered index and what you can expect back out from performance.

1. The Flavors of
Non-Clustered Indexes

2. Introduction
Jason
Strate
e: jstrate@pragmaticworks.com
e: jasonstrate@gmail.com
b: www.jasonstrate.com
t: StrateSQL
Resources
jasonstrate.com/go/indexing
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3. About Pragmatic Works
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Platform
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PDW
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Over 7,200 customers worldwide
Over 186,000 people in PW database for demand
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4. Caution
There will
be lots of
ice cream
pictures

5. Many Flavors

6. http://www.flickr.com/photos/rnljc/5334858173

7. http://www.flickr.com/photos/8566600@N07/2562797853

8. http://www.flickr.com/photos/amayu/5475537796

9. Non-Clustered Indexes
• Sorted key values
– One or more columns
– Key values only
– Pointers to Heap or
Clustered Index rows
– Non-LOB data
• Secondary data access
– Bridge to the data
• Operations
– Index scan
– Index seek
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10. Agenda
Vanilla
Sundae
Neapolitan
Rocky Road
Sugar Cone
Gelato
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11. VANILLA
http://www.flickr.com/photos/cowbite/3452599539/

12. Single Column Index
• Provides a secondary path to data
• Allows alternative paths for finding data
• One column is stored outside table
– Data is sorted by key
– Includes clustered index keys
• Focus on most used columns for filters
• Do not index every column
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13. Demo
SINGLE COLUMN
http://www.flickr.com/photos/cowbite/3452599539/

14. SUNDAE

15. Index Intersection
• Leverages multiple non-clustered indexes
• Filters on both indexes
• Returns the “intersection” of both indexes
Index
1
Index
2
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16. Demo
INDEX INTERSECTION

17. NEAPOLITAN

18. Multiple Column Index
• Two or more columns in the same index
• Index sorted from left to right
– Cannot skip columns to leverage sort
• Cover filters over multiple columns
– Or cover non-filtered columns
• Reduces number of indexes needed
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19. Demo
MULTIPLE COLUMN

20. ROCKY ROAD
http://www.flickr.com/photos/stuart_spivack/2069689027/

21. Included Columns
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Additional columns needed for queries
Typically data not included in index
Included columns brings in data pages
Store specific columns unsorted with index
Don’t included all columns
– Or even most
• Be cautious of update rate of data
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22. Demo
INCLUDED COLUMN
http://www.flickr.com/photos/stuart_spivack/2069689027/

23. SUGAR CONE

24. Filtered Indexes
• Add a WHERE clause to your index
• Changes the contents of the index
– Reduction in pages
– Reduction in size
– Lessen impact of index scan
• Unmatched Index warning
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25. Demo
FILTERED INDEXES

26. GELATO

27. Foreign Key Indexes
• All foreign keys should be indexed
– Not an index property
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Constraint leverages sorts on validation
Can reduce locking, blocking, and deadlocks
Common problem in many systems
Silent killer of the database
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28. FOREIGN KEYS

29. SUMMARY
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30. Summary
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You can get by on “vanilla” indexes
Indexes can vary in flavors
These flavors help improve your databases
Filtered indexes, included columns, and
multiple columns
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31. Learn More About Indexes
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32. For more information…
Name: Jason Strate
Email: jstrate@pragmaticworks.com
Blog: www.jasonstrate.com
Resource: jasonstrate.com/go/indexing
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