Solved

Left Outer Join with only 1 result

Posted on 2013-01-18
7
340 Views
Last Modified: 2013-01-18
I want to run a sql query using a left outer join, but I only want to return the first result, not all.

Table1:
ParentID 2

Table 2:
ID1 ParentID2
ID2 ParentID2
ID3 ParentId2

So when the rows are joined we have:

ParentID 2& Id1 only, not ID2 and ID3.

How do I do that?

I want to check the null value of the Id1 column to see if there is a record in that table, but I definitely don't want my parent row to show up 3 times, just the once.

thanks.
0
Comment
Question by:BobCSD
  • 3
  • 3
7 Comments
 
LVL 142

Expert Comment

by:Guy Hengel [angelIII / a3]
Comment Utility
Please view his article 8806085321953
0
 
LVL 142

Assisted Solution

by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 100 total points
Comment Utility
0
 
LVL 1

Author Comment

by:BobCSD
Comment Utility
that doesn't help.

A DISTINCT won't work because the value of the joined table's primary ID field is going to be unique.

I also don't see how a group by is going to resolve this.

Do you or anyone have any specific solutions to my problem?

thanks.
0
What Is Threat Intelligence?

Threat intelligence is often discussed, but rarely understood. Starting with a precise definition, along with clear business goals, is essential.

 
LVL 142

Expert Comment

by:Guy Hengel [angelIII / a3]
Comment Utility
the "ROWNUMBER()" method will work, and that is exactly what the article is about :)
0
 
LVL 1

Author Comment

by:BobCSD
Comment Utility
I feel I'm on a wild goose chase. I don't find any code in there using a JOIN and the snippet they have for mssql server doesn't show a row number. So unless you can dredge out of that article a snippet for me that works, I'm not closing this.
0
 
LVL 26

Accepted Solution

by:
Chris Luttrell earned 400 total points
Comment Utility
This is what andelIII is trying to show you in his article, you end up with something like this where you use the ROW_NUMBER() function to assign a rank (the row_number) per grouping (the Partition) to your secondary table so that when you join to it, you can match on just the first value.
SELECT * -- Pick the columns you want to see here
FROM dbo.Table1 T
LEFT OUTER JOIN (SELECT *, ROW_NUMBER() OVER (PARTITION BY ParentID ORDER BY ID) rn
				FROM dbo.Table2 T2) T2 ON T.ParentID = T2.ParentID AND rn = 1

Open in new window

You get results like this (I put an ID of 1 with no children to show it works both with and without child records)
Results
0
 
LVL 1

Author Closing Comment

by:BobCSD
Comment Utility
Thanks for all the additional effort!
0

Featured Post

6 Surprising Benefits of Threat Intelligence

All sorts of threat intelligence is available on the web. Intelligence you can learn from, and use to anticipate and prepare for future attacks.

Join & Write a Comment

Suggested Solutions

Title # Comments Views Activity
Truncate vs Delete 63 87
Problem with SqlConnection 5 109
TSQL - Rollup data set 7 29
SQL Help joining two tables 7 33
In this article I will describe the Detach & Attach method as one possible migration process and I will add the extra tasks needed for an upgrade when and where is applied so it will cover all.
How to leverage one TLS certificate to encrypt Microsoft SQL traffic and Remote Desktop Services, versus creating multiple tickets for the same server.
It is a freely distributed piece of software for such tasks as photo retouching, image composition and image authoring. It works on many operating systems, in many languages.
This demo shows you how to set up the containerized NetScaler CPX with NetScaler Management and Analytics System in a non-routable Mesos/Marathon environment for use with Micro-Services applications.

744 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

Need Help in Real-Time?

Connect with top rated Experts

16 Experts available now in Live!

Get 1:1 Help Now