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SQL Server FAQ - What Are Indexes

By: FYIcenter.com

(Continued from previous topic...)

What Are Indexes?

An index is a secondary database object associated with a table to improve the retrieval performance of rows from that table.

An index can be defined for a single column or multiple columns of a given table. If an index is defined on a single column of a table, the index can be viewed as ordered map between all values in that column and their row locations in the table. For examples, if you have table with a column called "company_num" and you created an index for that column. The contents of the table and the index may look like what is presented in the following picture:

As shown in the above picture, locating the rows of company_num = 17 can be done much faster through the index.

(Continued on next topic...)

1. What Are Indexes?
2. How To Create an Index on an Existing Table?
3. How To View Existing Indexes on an Given Table using SP_HELP?
4. How To View Existing Indexes on an Given Table using sys.indexes?
5. How To Drop Existing Indexes?
6. Is the PRIMARY KEY Column of a Table an Index?
7. Does the UNIQUE Constraint Create an Index?
8. What Is the Difference Between Clustered and Non-Clustered Indexes?
9. How To Create a Clustered Index?
10. How To Create an Index for Multiple Columns?
11. How To Create a Large Table with Random Data for Index Testing?
12. How To Measure Performance of INSERT Statements?
13. Does Index Slows Down INSERT Statements?
14. Does Index Speed Up SELECT Statements?
15. What Happens If You Add a New Index to Large Table?
16. What Is the Impact on Other User Sessions When Creating Indexes?
17. What Is Index Fragmentation?
18. What Causes Index Fragmentation?
19. How To Defragment Table Indexes?
20. How To Defragment Indexes with ALTER INDEX ... REORGANIZE?
21. How To Rebuild Indexes with ALTER INDEX ... REBUILD?
22. How To Rebuild All Indexes on a Single Table?
23. How To Recreate an Existing Index?