What are indexes?
The Indexes in the SQL Server are similar to the indexes in books. They help SQL Server to retrieve the data quickly.These are classified into clustered and nonclustered indexes.
The clustered index is a special type of index that reorders the way in which records in the table are physically stored. And hence, the table can have only one clustered index. The leaf node of a clustered index contains the data pages.
The nonclustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk. The leaf node of a nonclustered index does not include the data pages. Instead, the leaf nodes contain the index rows.