SQL joining to a table from two other tables in one go

Hi all,

I have inherited this query from a colleague.  I am not sure whether it is OK / recommended / downright wrong to join to a third table using fields from two other tables in the one join.

Can you advise please?

Colin BrazierAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

PortletPaulEE Topic AdvisorCommented:
It is quite acceptable to join like that.

Hard to give more advice without knowing more about the data & relationships; but is not "wrong"

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Colin BrazierAuthor Commented:
Ok thanks.  I don't see that too often and suspect I have duplicate rows so wanted to verify it.

Guy Hengel [angelIII / a3]Billing EngineerCommented:
I concur that this is perfectly possible (I use i almost every day).

if you have "duplicate rows", you may want to read up this article for explanations and solutions:http://www.experts-exchange.com/Database/Miscellaneous/A_3203-DISTINCT-vs-GROUP-BY-and-why-does-it-not-work-for-my-query.html
Yes, duplicates could be due to "cartesian product" or incorrect logic.
PortletPaulEE Topic AdvisorCommented:
Thanks for the points...

"duplicate rows" usually means "unexpected, and unwanted, repetition" that may not be due to that join. Most often it is many-to-one relationships that are the cause.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Microsoft SQL Server

From novice to tech pro — start learning today.