Use data validation rules to prevent duplicate entries in a range

- [Instructor] In Excel there's an easy and quick way … to find out if you have duplicates … within a given range of cells. … In this worksheet here, we're trying to find out … if there are any duplicates in column D … and the fastest way to do this is simply … select the column, in this case. … This is a list of over 700 entries. … We can go to Conditional Formatting on the Home tab … and as we slide it to Highlight Cell Rules, … off to the right and down Duplicate Values. … It immediately, and we might want to change the color scheme, … but we're seeing some results already … and you can see in cell D6 and cell D12, … we've got the same entry. … And obviously, that needs to be corrected. … But by clicking Okay we've finished the job here … and scrolling up and down you might see some others. … And note, of course, that sometimes the duplicate … could mean triplicate or quadruplicate, … whatever the word would be. … Sometimes we'll see this occurring elsewhere as well, too. … And you actually can sort on this basis, too, …