SQL with Manoj

–> Question:

According to MSDN, an index is an on-disk structure associated with a table or view that speeds retrieval of rows from the table or view.

In this definition, I don’t get what on-disk structure means.
 

–> My Answer:

Do not confuse with on-disk structure statement, not only index, a table is also an on-disk structure as all you data sits on-disk.

Check my response on you other similar question in MSDN TSQL forum.

Just like a table, an index is also on disk which can be built on top a table or separately.

– On top to restructure the whole table which is called the Clustered Index. Clustered Index is nothing but the table itself converted from a heap to a b-tree.

– Separately like a Non-Clustered index, which is a copy of the table with specific columns, created separately for performance reasons to read data will less columns.
 

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