3 way join SQL

Posted on 2008-10-27
Last Modified: 2012-05-05
I'm trying to connect 3 tables in my database: organizations, category_values and users_categories. If I change this:
where (uc.uid = '3' AND cv.catId='163')
to this:
where (uc.uid = '3')
I get all of the results I would expect. But adding the cv.catId I get 0 results (query runs with no errors). Is there something structurally wrong with my query?
$query = "select distinct o.orgId,, cv.catId
	from (organizations o join category_values cv
	on cv.orgId = o.orgId) join users_categories uc
	on uc.catId = cv.catId
	where (uc.uid = '3' AND cv.catId='163')
	order by ASC";

Open in new window

Question by:level9wizard
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
  • 2
LVL 11

Author Comment

ID: 22815236
As some more info, when I print row data the catId is the same for every row result. As if it's taking it from uc.catId and not cv.catId
LVL 143

Accepted Solution

Guy Hengel [angelIII / a3] earned 500 total points
ID: 22819994
what about this:
$query = "select distinct o.orgId,, cv.catId
        from organizations o join category_values cv
        on cv.orgId = o.orgId 
        left join users_categories uc
        on uc.catId = cv.catId and uc.uid = '3' AND cv.catId='163'
        order by ASC";

Open in new window

LVL 143

Expert Comment

by:Guy Hengel [angelIII / a3]
ID: 22819997
otherwise, you might not have any rows matching both criteria?!
LVL 11

Author Comment

ID: 22821413
I got the answer I was looking for thru IRC, thought i'd share...

$query = "SELECT o.orgId,, cv.catId FROM organizations o join (
SELECT DISTINCT cv2.orgId FROM users_categories uc JOIN category_values cv2 on uc.catId=cv2.catId WHERE uc.catId=200 and uc.uid=3 ) as d ON d.orgId=o.orgId
JOIN category_values cv ON d.orgId=cv.orgId
WHERE cv.catId='163'";
LVL 11

Author Closing Comment

ID: 31510383
The real solution to my problem is below, but I want to award you points for trying. Thanks!

Featured Post

How our DevOps Teams Maximize Uptime

Our Dev teams are like yours. They’re continually cranking out code for new features/bugs fixes, testing, deploying, responding to production monitoring events and more. It’s complex. So, we thought you’d like to see what’s working for us. Read the use case whitepaper.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Creating and Managing Databases with phpMyAdmin in cPanel.
Password hashing is better than message digests or encryption, and you should be using it instead of message digests or encryption.  Find out why and how in this article, which supplements the original article on PHP Client Registration, Login, Logo…

739 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question