Returnini non-unique data from a csv file

I’m looking for a way to sort a csv file on unique values in 3 columns. In addition to returning the unique data, I also need to know what the non-unique(duplicate) data was so I can report on it(i.e. what was dropped).

$uData below gives me the unique data I’m after -

$data = import-csv $InputFile -header("A","B","C","D","E","F","G")
$uData = import-csv $InputFile -header("A","B","C","D","E","F","G") | Sort C,D,E -unique 

To find the non-unique I tried a compare, though it is returning data that is unique, not that which was dropped -

compare-object $data $uData -passthru | Select C,D,E | ft

Any thoughts how how I can determine non-unique data in this scenario?


Nevermind, found my issue. It should be -

compare-object $zdata $Data -property C,D,E -passthru  | ft