Clustered Indexes

CLUSTERED INDEX

     Yes, Here I am going to explain about Indexes in SQL Server  as of my knowledge, I hope every one heard about Indexes but don't have a complete idea about it.

Ok, Let's start

     Basically Indexes are using for Query performance in SQL Server (actually not in SQL Server in all other Data Bases also using for performance only) , these are on-disk structure, and I read some where we can call as row store Index.

     Clustered Index will creates an Index Key and stored the data rows of the tables in order to clustered Index Key in sorting order (ascending or descending) , flow of the clustered index follows B-Tree structure.

    We can create using SQL Server Management Studio or T-SQL, a clustered Index can be rebuild or reorganize on demand to manage the Index Key order.

     When we create a table with the Primary Key that table will create along with Index Key, if table having the Clustered Index then those kind of tables called Clustered Tables, if that table doesn't have any Clustered Index then that we call as Heap Tables

    There can be only one Clustered Index per table, Table doesn't allow more than one Clustered Index

Syntax:

CREATE CLUSTERED INDEX <Index Name> ON <Table Name> (<Column Name>);   

Example:

CREATE CLUSTERED INDEX INDX_Emp_Tbl_Emp_Num ON dbo.Emp (Emp_Num);   

In Generally If table have more than 8 MB then only it goes to Index to get the data else it directly fetch the data from the table it self.

Soon I will update more Information on this

Please point if anything wrong, you can shoot a mail to : tthirmal@gmail.com