Prevent Duplicate Data Entry using Cell Validations

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We all know that data validation is a very useful feature in Excel. You can use data validation to create a drop-down list in a cell and limit the values user can enter. But, do you know that you can use data validation in a multitude of ways to prevent users from entering wrong data?

Here is a practical application: Prevent users from entering duplicate values in a range of cells.

For eg. you are making an invoice. Wouldn’t it be cool if Excel prompted you when you enter a duplicate line item so that increase the item quantity instead of repeating it.

Here is a 3 step tutorial to do just that.

Step 1: Identify the range of cells where you want only unique values to be entered

This is simple. All you have to do is find the range where you want to control the user input. Lets say the range is B4:B11

Step 2: Set up Data Validation to prevent duplicate entries

Select the range (B4:B11) and go to data validation (Excel 2007: Data Ribbon > Data Validation, or press ALT+AVV)

Using Data Validation to prevent DuplicatesNow, specify the validation type as “Custom”, this will allow us to use formulas to check for valid data. In our case, we need check if a particular entry is duplicated in the range B4:B11. This can be easily done using COUNTIF formula [learn COUNTIF Formula in plain English].

Go to the formula field and type the countif formula like this: =COUNTIF($B$4:$B$11,B4)<=1

Also, you can set up the “Error Alert” so that you can show a custom message when a duplicate value is typed, like “You have already added that product” message.

Data Validation - Error message

Once you set up error message, it will show up like this:

Data validation to prevent duplicates - error message example
Step 3: Sit back and Relax

The third step is all too familiar. Now that you have prevented duplicate entries in your spreadsheets you can sit back and relax. May be read a few more spreadcheats.

More kickass stuff on data validation (and working with duplicates) using excel

There are a ton of useful articles on the site related to data validation and working with duplicates using excel. Here is a sample. Get started and learn something useful today.

This post is part of our spreadcheats series (yes, the series is still going after one year 😛 )

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23 Responses to “Learn Top 10 Excel Features”

  1. Dwi Budi H says:

    What it looks like if excel without formula?? 🙂

    • philip says:

      It would be not excel it would just be fancy tables in which you could just use power point. (Chandoo) would Access be an alternative?

  2. Roy says:

    Awesome piece of work!!!

  3. Rich says:

    Great article.

    Chandoo - my biggest interest in the article was the awesome word-graphic at the top - where did you go to get it done into a shape?

  4. koushik says:

    Awesome Chandoo.. You need always needs coffee to start up with. BTW , how did u created the Heart Shaped picture filled with High Repetitive text in it .. Please put it on your Next blog ...

  5. Bob Watson says:

    Chandoo, good article. I’ve added a link to it from Connexion – our collection of the most useful and interesting spreadsheet-related articles from the web. See http://www.i-nth.com/resources/connexion

  6. ca.nkv says:

    Hi,

    Just one small question. Where the hell have been I in the past for not discovering this website sooner?

    I've lost a job interview recently where even though I had the subject knowledge, I was not upto their mark in Excel.

    Thank you for all the free tips, guidance and for creating this forum environment.

    [PS: I've just been through the site for the 1st time, and have signed up for the newsletter. You can expect pretty stupid questions from me soon]

  7. William Luke says:

    Hy Chandoo, you always inspire me with to explore something new in excel. This data structure table is only for excel 2007 or compatible to 2010. I recently installed latest excel version 2013 in my System and experience problems regarding operating according to previous one. I'm waiting your article relates to that excel version.

    Thanks

  8. Ankit Bansal says:

    Awesome article Mr. Chandoo and that is a awesome heart shaped pic you created. Great tips as well.

  9. [...] Learn Top 10 Excel Features | Chandoo.org – Learn Microsoft Excel Online. [...]

  10. Arvi says:

    Chandoo is awesome..

  11. Kevin Ko (student major in computer and tech.) says:

    Thanks, i got better, And i always get 90.50 in my grade card but now i get 96.50 i improved because of the tutorials you gave, Thank You Very Much Chandoo Guy.

  12. kiran says:

    Hi chandoo, i am intersted in seeing the video or step by step done procedure of analysing the comments and presenting in the data percentage steps. I think this one would be first step in finding out how generally happens data calculation. Thank you.

    As well i would like to know how to get that black shape art of your face which i see in chandoo. I am interested in making it for me.

  13. l3g4to says:

    Nice to see the features considered by Excel users to be most useful. It might be a good idea to also analyze StackOverflow Excel questions to see what keywords appear most often.

    Here are my top 10 Excel Features (for advanced users):
    http://www.analystcave.com/excel-10-top-excel-features/

  14. Nami says:

    Thanks a ton for this it totally helped with my homework ????

  15. pradip says:

    Very good effort

  16. Barb says:

    Thank you for this. Lots of learning in the links you've provided for this septuagenarian.

  17. Arun says:

    Pls send me new post

  18. Abhay says:

    Dude, your humor ? ?
    Loved your work.

  19. Sanjeev Khakre says:

    Hello Sir,

    I am Sanjeev Khakre and i from Indore City, India , I am your big follower and i have watch your videos and learnt a lots of excel trick or function and many more . thanks so much for all of your excellent support.

    Your excel knowledge is real awesome.

    Thanks
    Sanjeev

  20. Your work is excellent but pls willing to know more details about the features of microsoft excel

  21. philip says:

    Chandoo Would Access be a better alternative than VB?

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