Many blog posts and educational sites tell us to use
=countif($A$2:A2,A2)=1 in the selected range.
However, they don't explain it. And for me it doesn't work and since I can't understand it I can't debug it.
My understanding about Sheets is that
$ is for absolute reference. Thus
$A$2 means an absolute reference to the
A2 cell. For me the formula becomes
A2:A2 which is weird.
Can anyone please explain how this formula prevents the duplicates and what is the logic behind it? Thank you.