Learn T-SQL Querying

NonClustered Index Scan

A NonClustered Index Scan is effectively the same as a Clustered Index Scan. The difference is that the leaf level of a non-clustered index contains index pages rather than data pages, which means this is generally less I/O than a clustered index scan and is not analogous with a table scan.

The following is an example of a query executed in the AdventureWorks sample database with a NonClustered Index Scan:

SELECT LastName, FirstNameFROM Person.PersonWHERE FirstName = N'Andrew';

The query generates the following execution plan:

SQL Server will generally choose to do a non-clustered index scan when an index is present ...