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SQL Server FAQ - What Are Indexes
(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...)
- What Are Indexes?
- How To Create an Index on an Existing Table?
- How To View Existing Indexes on an Given Table using SP_HELP?
- How To View Existing Indexes on an Given Table using sys.indexes?
- How To Drop Existing Indexes?
- Is the PRIMARY KEY Column of a Table an Index?
- Does the UNIQUE Constraint Create an Index?
- What Is the Difference Between Clustered and Non-Clustered Indexes?
- How To Create a Clustered Index?
- How To Create an Index for Multiple Columns?
- How To Create a Large Table with Random Data for Index Testing?
- How To Measure Performance of INSERT Statements?
- Does Index Slows Down INSERT Statements?
- Does Index Speed Up SELECT Statements?
- What Happens If You Add a New Index to Large Table?
- What Is the Impact on Other User Sessions When Creating Indexes?
- What Is Index Fragmentation?
- What Causes Index Fragmentation?
- How To Defragment Table Indexes?
- How To Defragment Indexes with ALTER INDEX ... REORGANIZE?
- How To Rebuild Indexes with ALTER INDEX ... REBUILD?
- How To Rebuild All Indexes on a Single Table?
- How To Recreate an Existing Index?