Index In SQL Server Part VI

Index In SQL Server

Index :

  • Indexes are used to improve the performance of  searching, Because they are in sequential format it helps the searching operation.
  • An index is an on-disk structure associated with a table or view that speeds retrieval of rows from the table or view.
  • An index contains keys built from one or more columns in the table or view.
  • These keys are stored in a structure (B-tree) that enables SQL Server to find the row or rows associated with the key values quickly and efficiently.
A table or view can contain the following two types of indexes :


1) Clustered Index :
  • Clustered Index arranges the indexes in the form of the Balanced Tree Structure(B-Tree).
  • In SQL server clustered index is created automatically, when a primary key is created.
  • There can be only one clustered index per table, because the data rows themselves can be stored in only one order.  
Creating Clustered Index in SQL Server : 

1) Go to Design of a table, then Right click on column and select Indexes/Keys :

2) The Table Designer set Create As Clustered as Yes,then Clustered Index is created Successfully :

2) Non-Clustered Index :

  • In Non-Clustered Index, it also arranges a Balanced tree structure.
  • There can be multiple non-clustered index per table, because the data rows themselves can be stored in multiple order.  
Creating Non-Clustered Index in SQL Server : 

1) Go to Design of a table, then Right click on column select and open Indexes/Keys then click Add & Select the column name :

2) Select type to index :

SQL Plan :

  • The SQL plan is nothing but is the plan by SQL server created while executing.
  • Then the query is written completely.
  • You can directly click the “Display Estimated Execution Plan” toolbar button :

Example :


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