1. Indexes: The Basics
Kathi Kellenberger

3. Good things come in small packages…

4. Heaps B-Trees Two Types of Tables
Heaps – not logically organized. Table without a clustered index
B-Trees – used for clustered indexes and non-clustered indexes
Data is organized by the key
Heaps
B-Trees

5. Heap M S D X A T F
When looking for a value within a heap, have to scan the data to find it.
If I am looking for A, I have to look at M, S, D, X to get to A
No organization
Good in some circumstances like loading staging tables

6. B-Tree M T D A F S X Balanced tree Hierarchy
When I want to find a value, just have travel down the levels
To find A, I start at M, is A less than M? Go to D. Is A Less than D? Go to A.
When you add a clustered index to a table, it is organized as a B Tree A F S X

7. Find the Number Game
How long to find a number when the numbers are random?
How long when they are organized in a b-tree structure?

8. Clustered Index StructureM D T
Non-Leaf Levels A F S X A D F
Leaf Level M S T X
Non-leaf levels contain the cluster key
Leaf levels contain the data pages: cluster key + non-key columns

9. The best cluster key is ever-increasingM S D X A T F
You can see lots of opinions about clustered index key.
The best key is ever increasing. That means a date or ID column

10. The best cluster key is narrow and unique

11. The Best Clustered Key is Static
CHANGES

12. Non-Clustered Indexes

13. Non-Clustered Indexes

14. Non-clustered Index StructureM D T
Non-Leaf Levels A F S X A D F
Leaf Level M S T X
Non-leaf levels contain the Index Key
Leaf levels contain the Index Key, Pointer to table row and Included Columns

15. Column Order Is Important!
LastName
FirstName
City

16. Key Lookups
When the index just isn’t enough

17. Covering Indexes

18. Best Practices Index foreign keys Index keys used in searches
Avoid duplicate indexes
Avoid indexes that are rarely used – unless there is a business reason
DO NOT BLINDLY FOLLOW RECOMENDATIONS

19. Index Maintenance Maintenance Wizard Scripts Reorganize Rebuild
Rebuild at 30% fragmentation
Reorg > 10% and < 30%
Ignore small tables
Record what is done

20. Resources Glenn Berry Blog: http://sqlserverperformance.wordpress.com/
Expert Performance Indexing for SQL Server 2012 by Jason Strate (Apress)
Ola Hallengren maintenance solution:
Duplicate index script: duplicate-indexes-on-sql-server/