An Index is a tree structure that allows direct access to a row in a table. Indexes can be classified based on their logical design or on their physical implementation.
The Logical classification groups indexes from an application perspective while the physical classification is derived from the way the indexes are stored
An index is a schema object that can speed up the retrieval of rows by using pointers. If you do not have an index then a full table scan occurs. Its purpose is to reduce disk I/O by using an indexed path to locate data quickly. If a table is dropped the corresponding indexes are also dropped. In case of doubt contact me : bobby_1020@hotmail.com
