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April 1, 2013 by rfid

One of nice post on Oracle, Written by ARUMAN Oracle DBA



           Indexes are database objects that you can create to improve the performance of the query.Indexes can reduce disk I/O by using a rapid path access method to locate data quickly.Indexes are used and maintained by oracle server automatically.Indexes can be created explicitly or automatically.If you do not have an index on column,then full table scan occurs.

                   Indexes are logically and physically independent of the table that they index.This means that they can be created or dropped at any time and have no effect on base tables or other indexes. Create an index on one or more columns by issuing the CREATE INDEX statement.

CREATE INDEX emp_last_name_idx

ON                  employees(last_name);

CREATE INDEX  succeeded.

In the above example emp_last_name_idx is the index name and employees is the table name and last_name is the column name.

                  When you drop a table,corresponding indexes are also dropped.You…

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