index in sql

Index:-
An index is a schema object that can speed up the retrieval of rows by using a pointer. Indexes can be created explicitly or automatically. If we do mot have an index on the column, then a full table scan will occur. An index provides direct and fast access to rows in a table. Its purpose is to reduce the necessity of disk I/O by using an indexed path to locate data quickly. The index is used and maintained automatically by the Server. Once an index is created, no direct activity is required by the user. Indexes are logically and physically independent of the table they index . This means that they can be created or dropped at any time and have no effect on the base tables or other indexes. When we drop a table, corresponding indexes are also dropped.<a href="http://www.netnic.org/index-in-sql/"> More Information click here </a>