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Clustered and nonclustered indexes share many of the same internal structures, but they're fundamentally different in nature. Watch Microsoft Certified IT Professional Jon Seigel explain the similarities and differences of clustered and nonclustered indexes, using a real-world example to show how these structures work to improve the performance of SQL queries.
Sample index data is from the AdventureWorksLT2008R2 sample database
Article source from : https://voluntarydba.com/2014/01/07/clustered-vs-nonclustered-index-internal-structures-video/