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

 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
 Oracle Support

 SQL Tuning

 Oracle UNIX
 Oracle Linux
 Remote s
 Remote plans
 Application Server

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

 Remote S


 Consulting Staff
 Consulting Prices
 Help Wanted!


 Oracle Posters
 Oracle Books

 Oracle Scripts

Don Burleson Blog 







Oracle ORDER BY tips

Oracle Database Tips by Donald BurlesonFebruary 7,  2015

Sorting with Oracle ORDER BY

Sometimes it is necessary that the rows returned from your query to be in a specific order.  For example, I might want scores from high to low or names in alphabetical order.  By default, the database will sort data ascending, smallest to largest.  Words are sorted alphabetically.  NULLs cannot be sorted, they will be listed as found at the bottom of the results.   

To sort the results set, we use the ORDER BY clause.   

order by author_last_name;

The Oracle ORDER BY clause must be used if you require that the rows be sorted.  The Oracle database, by default, will not sort the results set, nor does it store rows in a table in a specific order.

The Oracle ORDER BY clause is important because internally, the Oracle database uses a HEAP organized table as its default table.  A HEAP table stores new data in the first available slot.  Once you start adding and deleting rows in your table, the row order becomes random.  Different queries (and for that matter, the same query run at different times) will use different execution plans to retrieve the requested data.  Thus, the results can be ordered differently if you do not use the Oracle ORDER BYclause.   

Let's look at the AUTHOR table.   

The only way to insure that the rows are ordered is to use the Oracle ORDER BY clause.  Also, sorting is always performed last.  It makes no sense to sort an intermediate row set that we will never see.   

 Let's now take a look at the Oracle ORDER BY clause. 

order by author_last_name;

In the first query, we retrieved the author_last_name from the author table.  The rows were returned as the database found them.  In the second example, we executed the same query except that we used the Oracle ORDER BY clause to order them alphabetically by last name.  Notice that the default is ascending.  In the next example, we again selected the author's last name, but we used Oracle ORDER BY to order them by author_key descending. 

order by author_key desc;

Notice in the example above that I did not select the author_key even though I used it in the Oracle ORDER BY clause. 


Related Oracle ORDER BY information:
Sorting, Grouping, Table Joins, and Subqueries

Internals of Oracle Sort Operations





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 -  2017

All rights reserved by Burleson

Oracle ® is the registered trademark of Oracle Corporation.

Remote Emergency Support provided by Conversational