What is index ?

Index is a pointer in sql server to retrieve the data faster from database.

It’s a physical structure containing pointers to data.

Its created in existing tables to locate rows more quickly and efficiently.

Types of Index:

a)    Clustered Index : It contains only one index ie: Creating a primary key for the table.
Physical sorting of data in the storage media.

b)    Non-Clustered Index :  A table can contains 249 non-clustered index, It can be created outside of the database tables , that contain a sorted list of references to the table itself.