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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21 Responses to “How to Filter Odd or Even Rows only? [Quick Tips]”

  1. Vijay says:

    Infact, instead of using =ISEVEN(B3), how about to use =ISEVEN(ROW())

    So it takes away any chance of wrong referencing.

  2. Hui... says:

    I like Daily Dose of Excel

  3. vimal says:

    I like it.

  4. Luke M says:

    Just a heads up, you do need to have the Analysis ToolPak add-in activated to use the ISEVEN / ISODD functions. An alternative to ISEVEN would be:
    =MOD(ROW(),2)=0

  5. Debbi says:

    rather than use a formula, couldn't you enter "true" in first cell and "false" in the second and drag it down and than filter on true or false.

  6. Paul S says:

    Just for clarification, is Ashish looking to filter by even or odd Characters or rows?

  7. Fred says:

    so many functions to learn!

  8. Istiyak says:

    Nice support by chandoo and team as a helpdesk. Give us more to learn and make us awesome. Always be helpful.......

  9. Arps says:

    In case you want to delete instead of filter,

    IF your data is in Sheet1 column A
    Put this in Sheet2 column A and drag down
    =OFFSET(Sheet1!A$1,(ROWS($1:1)-1)*2,,)
    (This is to delete even rows)

    To delete odd rows :
    =OFFSET(Sheet1!A$2,(ROWS($1:1)-1)*2,,)

  10. Pippa says:

    If your numbered cells did not correspond to rows, the answer would be even simpler:
    =MOD([cell address],2), then filter by 0 to see evens or 1 to see odds.

  11. Matthew D. Healy says:

    I sometimes do this using an even simpler method. I add a new column called "Sign" and put the value of 1 in the first row, say cell C2 if C1 contains the header. Then in C3 I put the formula =-1 * C2, which I copy and paste into the rest of the rows (so C4 has =-1 * C3 and so forth). Now I can just apply a filter and pick either +1 or -1 to see half the rows.

    Another way, which works if I want three possibilities: in C2 I put the value 1, in C3 I put the value 2, in C4 I put the value 3, then in C5 I put the formula =C2 then I copy C5 and paste into all the remaining rows (so C6 gets =C3, C7 gets =C4, etc.). Now I can apply a filter and pick the value 1, 2, or 3 to see a third of the rows.

    Extending this approach to more than 3 cases is left as an exercise for the reader.

  12. Paulo says:

    Another way =MOD(ROW();2). In this case, must to choose betwen 1 and 0.

  13. Makhan Butt says:

    very different style Odd or Even Rows very easy way to visit this site

    http://www.handycss.com/tips/odd-or-even-rows/

  14. Terhile says:

    Thanks for the tip, it worked like magic, saved having to delete row by row in my database.

  15. majid says:

    Thankssssssssssssssss

  16. Bhanu says:

    Hi Chandoo- First of all thanks for the trick. It helped me a lot. Here I have one more challenge. Having filtered the data based on odd. I want to paste data in another sheet adjacent to it. How can I do that?
    For Example-
    A 1 odd
    B 3 odd
    C 4 even
    D 6 even
    I have fileted the above data for odd and want to copy the "This is odd number" text in adjacent/next sheet here. How can I do that. After doing this my data should look like this
    A 1 odd This is odd number
    B 3 odd This is odd number
    C 4 even
    D 6 even

  17. Adriana says:

    Hi! Could you please help me find a formula to filter by language?
    Thank you!

  18. avinash says:

    Chandoo SIR,

    I HAVE A DATA IN EXCEL ROWS LIKE BELOW IS THERE ANY FORMULA OR A WAY WHERE I CAN INSTRUCT I CAN MAKE CHANGES , MEANS I WANT TO WRITE ONLY , THE FIG IS FRESH, BUT IN BELOW ROW IT WILL AUTOMATICALLY TAKE THE SOME WORDS FROM FIGS AND MAKE IN PLURAL FORM , WHILE USING '' ARE'' LIKE BELOW

    The fig is fresh - row 1
    Figs are fresh - row 2
    The Pomegranate is red - row 3
    Pomegranates are red - row 4

  19. Arshad Hussain Shah says:

    =IF(EVEN(A1)=A1,"EVEN - do something","ODD - do something else") with iferron (for blank Cell)

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