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 


 

 

 


 

 

 
 

qb_name hint tips

Oracle Database Tips by Donald BurlesonMay 22, 2016

Question: What does the 10g qb_name hint do?  Can you describe when to use the qb_name hint?

Answer:  The cost-based optimizer tries to eliminate multiple select statements in a complex query by merging in-line views and subqueries into a single SQL statement.  In Oracle parlance, each in-line view and subquery is a separate and distinct "query block".

Solely for debugging purposes, Oracle has created the query block name (qb_name) hint to allow you to clearly see the individual query blocks in a complex SQL query that has subqueries (or in-line views).

For example, Oracle un-nests some correlated subqueries and replaces it with a single anti-join operation.  Ti see this, you can add a qb_name hint and then reference this nased query block in a no_unnest hint:

select /*+ no_unnest(@nested_query) */
*
from
t1
where
not exists
(
select /*+ qb_name(nested_query) */
null
from
t1 t1_inner
where
t1_inner.id = t1.id
);

Oracle experts use the qb_name hint to plant "markers".  These markers have two purposes:

1 - The markers make reading complex execution plans (subqueries) easier to read.

2 - The qb_name hint allows hints to be applied to subqueries.


   
Oracle Training from Don Burleson 

The best on site "Oracle training classes" are just a phone call away! You can get personalized Oracle training by Donald Burleson, right at your shop!

Oracle training
 
 


  Oracle consulting and training

 

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 -  2016

All rights reserved by Burleson

Oracle ® is the registered trademark of Oracle Corporation.


 

��  
 
 
Oracle Training at Sea
 
 
 
 
oracle dba poster
 

 
Follow us on Twitter 
 
Oracle performance tuning software 
 
Oracle Linux poster