How does Excel set prompts to enter specific duplicate data in a column?

How does Excel set the prompt in a column to enter specific duplicate data? When we use Excel, we often need to set up a column of data, do not allow the input of specific duplicate data, below a brief description of how to do, a look at it!

Open the Excel program interface, enter the main interface, enter the data

Then select the data you want for the column, and click the Data tab on the toolbar

In the Data options interface, click the Data Validation button option

In the pop-up data validation interface, click on the Validation conditions dropdown box option, click the "Custom" option

Enter =COUNTIF in the formula column ($A $ $A $, $A $) = 1, which is 1 to 15 rows in cell A, compared to the first row $a1$1, or 1 if not the same

Then click on the "Error Warning" tab, enter some error message, then click OK

And then enter in the range of the specified cells, and the same number as the first line, we can see the message

The above is how Excel set in a column prompts to enter a specific data de-duplication method Introduction, the operation is very simple, we have learned? Hope to be helpful to everybody!