RE: Advanced SQL
- From: "Ryan Stevens" <RYSteve@xxxxxxxxxxx>
- To: <programmingblind@xxxxxxxxxxxxx>
- Date: Fri, 26 Aug 2011 06:16:25 -0400
Hi, Jeff,
You may also want to try a full outer join rather than either a left or
right outer join. For example,
SELECT Topic.TopicName, Action.ActionName FROM Topic
FULL JOIN Relationship ON Topic.ID = Relationship.TopicID
FULL JOIN Action ON Relationship.ActionID = ActionID
If you need unlinked topics, but not unlinked actions, you could also left
join topic into a subquery made between Relationship and Action, such as
SELECT Topic.TopicName, ActionByTopic.ActionName FROM Topic LEFT JOIN
(SELECT Relationship.TopicID, Action.ActionName FROM Relationship
INNER JOIN Action ON Relationship.ActionID = Action.ID) AS ActionByTopic
ON Topic.ID = ActionByTopic.TopicID
HTH
Ryan Stevens
-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Jeff Berwick
Sent: Thursday, August 25, 2011 7:10 PM
To: programmingblind@xxxxxxxxxxxxx
Subject: Advanced SQL
Hi Listers,
I need some sql assistance.
I have three tables that are connected in a many to many relationship. The
three tables are:
topic, relationship (the many to many table) and Action.
I want to show all the relationships but, if there are no relationships I
need to still show the Topics. Sample tables might look like:
Topic
++++++
id
+++++
1
2
3
4
Relationship
+++++++
topic_id | action_id
+++++++
1 | 1
3 | 2
4 | 3
4 | 4
Action
++++++
id
+++++
1
2
3
4
I know I need to use a left outer join at some point but, can't get this
figured out. Any assistance is welcome and appreciated.
TIA,
Jeff
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