Gmail sheets and data integrity

Say, I have a Gmail sheet with name, surname and telephone number . I am trying to ensure that no duplicates of the telephone number are created. Apparently the users search before they enter each new entry, but sometimes they forget to do this and end up with duplicates. Is there a way to enforce data integrity as in a database by creating a primary key structure?
shaunwinginAsked:
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.

dsackerContract ERP Admin/ConsultantCommented:
You will have to use an adjacent column for this.

For instance, in C1, put in the following formula:

=ARRAYFORMULA( IF(ISBLANK(B:B) ,  IFERROR (1/0) , IF( COUNTIF (B:B,B:B)>1 , 1 , IFERROR(1/0))))
Now, put a heading in B1, perhaps something like "My Value".

In B2, enter 1
In B3, enter 2
In B4, enter 3
In B5, enter 4
In B6, enter 1   (your first duplicate value)

:)
0

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
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
Google Apps

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.