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SQL Server FAQ - Primary Key - Default Indexes of Tables
(Continued from previous topic...)
Is the PRIMARY KEY Column of a Table an Index?
If you define a primary key on a table, an index for the primary key
column will be created by default.
The tutorial exercise below shows you the index created as part of the
primary key column of "fyi_links":
-- Drop the old table, if needed
DROP TABLE fyi_links;
-- Create a table with primary key
CREATE TABLE fyi_links (
id INT PRIMARY KEY,
url VARCHAR(80) NOT NULL,
created DATETIME NOT NULL DEFAULT(getdate())
-- Create an index for column "url"
CREATE INDEX fyi_links_url ON fyi_links (url);
-- View indexes
EXEC SP_HELP fyi_links;
index_name index_description keys
----------------------- -------------------------- ----
fyi_links_url nonclustered located url
PK__fyi_links__239E4DCF clustered, unique, primary
key located on PRIMARY id
Notice that the index created as part of the primary key is named
by SQL Server as "PK__fyi_links__239E4DCF".
(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?