Call now: 252-767-6166  
Oracle Training Oracle Support Development Oracle Apps

 
 Home
 E-mail Us
 Oracle Articles
New Oracle Articles


 Oracle Training
 Oracle Tips

 Oracle Forum
 Class Catalog


 Remote DBA
 Oracle Tuning
 Emergency 911
 RAC Support
 Apps Support
 Analysis
 Design
 Implementation
 Oracle Support


 SQL Tuning
 Security

 Oracle UNIX
 Oracle Linux
 Monitoring
 Remote s
upport
 Remote plans
 Remote
services
 Application Server

 Applications
 Oracle Forms
 Oracle Portal
 App Upgrades
 SQL Server
 Oracle Concepts
 Software Support

 Remote S
upport  
 Development  

 Implementation


 Consulting Staff
 Consulting Prices
 Help Wanted!

 


 Oracle Posters
 Oracle Books

 Oracle Scripts
 Ion
 Excel-DB  

Don Burleson Blog 


 

 

 


 

 

 
  Oracle Database Tips by Donald Burleson

Creating Indexes

The same format is used no matter which type of index you are creating.

Create unique|bitmap index <index name> on
<table name> (col1, col2, col3,); 

A unique index was covered in the discussion of constraints as well as uses to both speed queries and enforce that each value in the column is unique. 

create unique index auth_contract on  author(author_contract_nbr);

create bitmap index bk_auth on
  book_author(book_key, author_key); 

create index half_sales on
  sales (quantity/2);
 

If you do not define the type of index, the database creates a non-unique b-tree index. 

If you decide that you want to change an index, from unique to non-unique for example, you have to drop the current index and recreate it in the new type.  You can rebuild indexes using the ALTER INDEX command.  When you rebuild an index, the database uses the current index if it is valid to create the new index.  Once the new index is created, the old index is dropped. 

If you specify online, the database will continue to use the old index until the new one is completed and then switches to the new index.  You can also use the rebuild to move the index to another tablespace.

alter index bk_auth rebuild online;
alter index bk_auth rebuild tablespace indx_ts;

If the current index is not valid, then the database rebuilds the index from the original table.  Invalid indexes are not used.  An index becomes invalid when the rowids in the index no longer match the rowids in the table.  If I rebuild a table, all the indexes created on that table will be marked invalid and must be rebuilt.

As a last point on indexes, you must be careful in indexing your database.  Each index adds overhead, having to be updated with every change to that column in the table.  If your database uses static data and only select queries, then over indexing will not hurt performance.  But, most databases have a mix of INSERTs, UPDATEs, DELETEs and SELECTs.  Too many indexes can have a significant negative impact on INSERTs, UPDATEs, and DELETEs.

There are many other objects in the Oracle database, but we are focusing on those that impact SQL.  Most of the other objects belong in the realm of the DBA and are beyond the scope of this book.

 
Get the Complete
Oracle SQL Tuning Information 

The landmark book "Advanced Oracle SQL Tuning  The Definitive Reference"  is filled with valuable information on Oracle SQL Tuning. This book includes scripts and tools to hypercharge Oracle 11g performance and you can buy it for 30% off directly from the publisher.
��  
 
 
Oracle Training at Sea
 
 
 
 
oracle dba poster
 

 
Follow us on Twitter 
 
Oracle performance tuning software 
 
Oracle Linux poster
 
 
 

 

Burleson is the American Team

Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise. All legitimate Oracle experts publish their Oracle qualifications.

Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  

and include the URL for the page.


                    









Burleson Consulting

The Oracle of Database Support

Oracle Performance Tuning

Remote DBA Services


 

Copyright © 1996 -  2020

All rights reserved by Burleson

Oracle ® is the registered trademark of Oracle Corporation.