Solved

UPDATE a field from a COUNT in another table

Posted on 2009-07-16
4
520 Views
Last Modified: 2012-05-07
Hi

I want to do something like this:

UPDATE tableA SET Afield1 =(SELECT COUNT(Bfield1) FROM tableB WHERE NOT Bfield2 GROUP BY Bfield3)

But 2 problems:
1) Its returning an error telling that I have 2 returning rows of subquery, and
2) I see a problem because where is the join? It should update Afield1 for each Arecord based on a count in Btable. There have to be a connection between the 2 tables via the primary & foreign key IDs in each table.

How should my MySQL update statement look in order to work?
0
Comment
Question by:loopstudio
  • 2
4 Comments
 

Author Comment

by:loopstudio
ID: 24871029
I want to JOIN by Afield2 and Bfield3
0
 
LVL 45

Accepted Solution

by:
Kdo earned 125 total points
ID: 24871129
Hi loop,

The subselect in your update will return a row for every value of Bfield3 in tableB.  The query doesn't know how to match the result to tableA so it does the only thing it know to do -- attempt to update TableA.  But since the query returned multiple row, the DBMS is trying to store multiple rows in a single variabe.  Hence the error.

In the subquery, join the tables.  WHERE tableA.Afield = tableB.Bfield3.  The rest of the query looks fine.


Good Luck,
Kent
0
 

Author Comment

by:loopstudio
ID: 24871140
sorry for any inconvenience, I just found the problem myself
thanx :)
0
 
LVL 17

Expert Comment

by:Suat Ozgur
ID: 24872009
To moderator's review:
Provided solution by Kent is correct and it provides exact solution to the problem.
However, I see loop posted cancel request at the same time answer provided by Kent but didn't provide the found solution.

There is no point to keep this question in the database in case it wouldn't point to a solution. Therefore my suggestion would be accepting Kent's solution with 0 point (unless loop comes up with something else) but refunding points. This way, people searching for "update description by using join" would be able to see a nice comment.
0

Featured Post

What is SQL Server and how does it work?

The purpose of this paper is to provide you background on SQL Server. It’s your self-study guide for learning fundamentals. It includes both the history of SQL and its technical basics. Concepts and definitions will form the solid foundation of your future DBA expertise.

Question has a verified solution.

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

Both Easy and Powerful How easy is PHP? http://lmgtfy.com?q=how+easy+is+php (http://lmgtfy.com?q=how+easy+is+php)  Very easy.  It has been described as "a programming language even my grandmother can use." How powerful is PHP?  http://en.wikiped…
If you find yourself in this situation “I have used SELECT DISTINCT but I’m getting duplicates” then I'm sorry to say you are using the wrong SQL technique as it only does one thing which is: produces whole rows that are unique. If the results you a…
I designed this idea while studying technology in the classroom.  This is a semester long project.  Students are asked to take photographs on a specific topic which they find meaningful, it can be a place or situation such as travel or homelessness.…
Delivering innovative fully-managed cloud services for mission-critical applications requires expertise in multiple areas plus vision and commitment. Meet a few of the people behind the quality services of Concerto.

911 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

23 Experts available now in Live!

Get 1:1 Help Now