Leave a comment

April 1, 2013 by rfid

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

oraclegurugoswami

 Index

           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…

View original post 507 more words

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: