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SQL Server FAQ - Creating an Index for Multiple Columns

By: FYIcenter.com

(Continued from previous topic...)

How To Create an Index for Multiple Columns?

An index for multiple columns works similarly to a sorting process on multiple columns. If an index is defined for two columns, the index key is composed by values from those two columns.

A multi-column index will be used to speed up the search process based on the same columns in the same order as the index definition. For example, if you define an index called "combo_index" for "url" and "counts". "combo_index" will be used only when searching or sorting rows by "url" and "counts".

The tutorial exercise below shows you how to create an index for two columns:

-- Create an index for two columns
CREATE INDEX combo_index ON fyi_links (url, counts);

-- View indexes
EXEC SP_HELP fyi_links;
index_name         index_description               keys
-----------------  --------------------------      ----
fyi_links_created  nonclustered located on PRIMARY created
fyi_links_url      clustered located on PRIMARY    url
combo_index        nonclustered located on PRIMARY url, counts

-- Drop the index
DROP INDEX fyi_links.combo_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?

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