Indexes-Indexing is way to sort and search records in the table. It will improve the speed of locating and retrieval of records from the table.It can be compared with the index which we use in the book to search a particular record.
In Sql Server there are two types of Index
1) Clustered Index
2) Non Clustered Index
Clustered Index:- Clustered index physically stored the data of the table in the order of the keys values and the data is resorted every time whenever a new value is inserted or a value is updated in the column on which it is defined.
In a table only 1clustered index is possible.
In a clustered Index, the leaf node contains the actual data.
Non Clustered Index:- In case of Non clustered index it create a sperate list of key values (or created a table of pointers) which points towards the location of the data in the data pages.
In a table, we can create 249 Non clustered indexes in SQL 2005 and 999 Non clustered indexes in SQL Server 2008 and onward.In a non clustered Index, the leaf node contains the pointer to the data rows of the table.