Clustered indexes sort and store the data rows in the table or view based on their key values.
https://msdn.microsoft.com/en-IN/library/ms190457.aspx
It means if a table has a clustered index, then the rows of that table will be stored on disk in the same exact order as the clustered index.
Secondly, the leaf nodes of a Clustered Index contains data pages of the table on which it is created.
https://technet.microsoft.com/en-us/library/ms177443%28v=sql.105%29.aspx
So, my question is that same data is stored in the Clustered Index and table on which it is created?
If Yes, then what is the need to sort the table in the same order as clustered index? Because clustered index itself stores the row-level data in it’s leaf nodes.
And if NO, then what is the actual theory behind the creation of Clustered Index?
