I'd use just MATCH -- let's say you've got data in column A of both sheets.
=MATCH(A1,'Other Sheet Name'!A:A,0)
The above in, say, B1 then copied down to end of column-A data.
The return of as number signifies that that Ax value was found on the other sheet [ the number will be the row number of the 1st match ].
A eturn of #N/A signifies no match was found.