Here below is a personnel data table:

Judge whether there are duplicate data, if so, fill in 1 in corresponding Dup field, otherwise fill in 0 (the judging basis is that the data in the Name field are the same). Enter the formula in cell E2:

=spl("=if(?1.conj().select(~==?2).count()>1,1,0)",B$2:B$7,B2)

Then drag E2 down to every relevant row:

esProc Desktop and Excel Processing
9.1 Judge duplication of simple members
9.3 Judge duplication of row-based data - by whole row