We help IT Professionals succeed at work.

SQL Query to get orphaned nodes

313 Views
Last Modified: 2014-11-11
Hi all,
I have an interesting query that I am trying to create...

I have a table that contains entities, each of these *may* have a parent (only single level)

What I would like to do is query the table to find entries that say they have a parent, but the parent entry does not exist.

tblData
ID, DESCRIPTION, PARENT
'A','Main Parent','-'
'B','First Child','A'
'C','Second Child','A'
'D','Another Parent','-'
'E','An Orphan','Z'

In this example, I would like to execute a query to get the record relating to 'E'

I've tried a few ways, but can't get it to work!!!

Any ideas would be very much appreciated..

Thanks a lot,

James
Comment
Watch Question

CERTIFIED EXPERT
Commented:
This one is on us!
(Get your first solution completely free - no credit card required)
UNLOCK SOLUTION
Phillip BurtonDirector, Practice Manager and Computing Consultant
Awarded 2014
Top Expert 2014
Commented:
This one is on us!
(Get your first solution completely free - no credit card required)
UNLOCK SOLUTION
ste5anSenior Developer
CERTIFIED EXPERT

Commented:
You should use a foreign key constraint to avoid this situation.

SELECT  C.*
FROM    #tblData C
        LEFT JOIN #tblData P ON C.PARENT = P.ID
WHERE   P.ID IS NULL;

Open in new window

Author

Commented:
Perfect!!! Thanks :-)
Hope it is okay to split points equally as there was only 1 minute between posts!

Gain unlimited access to on-demand training courses with an Experts Exchange subscription.

Get Access
Why Experts Exchange?

Experts Exchange always has the answer, or at the least points me in the correct direction! It is like having another employee that is extremely experienced.

Jim Murphy
Programmer at Smart IT Solutions

When asked, what has been your best career decision?

Deciding to stick with EE.

Mohamed Asif
Technical Department Head

Being involved with EE helped me to grow personally and professionally.

Carl Webster
CTP, Sr Infrastructure Consultant
Empower Your Career
Did You Know?

We've partnered with two important charities to provide clean water and computer science education to those who need it most. READ MORE

Ask ANY Question

Connect with Certified Experts to gain insight and support on specific technology challenges including:

  • Troubleshooting
  • Research
  • Professional Opinions
Unlock the solution to this question.
Join our community and discover your potential

Experts Exchange is the only place where you can interact directly with leading experts in the technology field. Become a member today and access the collective knowledge of thousands of technology experts.

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

OR

Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.