How to Prevent Duplicate Data Entries in Google Sheets | Google Sheets Tutorials
The steps to prevent duplicate entries in Google Sheets are as follows:
1. Highlight or select the column for which you want to be marked to prevent duplicate entries/data,
2. Select the Data menu, then select the "Data Validation" menu, and click the "Add rule" button,
3. Then change the "Dropdown" in Criteria to "Custom formula is". Type the formula "=COUNTIF(selected cell/data and add the $ character between the letters and the column number, followed by the first cell/column of the data)=1" in the formula column. For example, if we want to prevent duplicate entries/data in cell/column A2 to cell/column A10, we can type the formula "=COUNTIF(A$2:A$10, A2)=1".
4. Check the "Show help text for a selected cell" box, then type the message you want as a reminder that the data is duplicate data,
5. After that, you select "Reject the input", and click the "Done" button,
6. Try to type the same data in the column that has been set, if the data is the same, a reminder message will appear that the data is duplicate,
7. Done.
Hope it is useful.