Finding matches (

[GARY]

Col A has 2500 cells and Col B has 1 million cells.

How can I find the cells in Col A whose contents exactly match those
in Col B?
How should the formula be written?

 

[Max]

Assume data in row2 down
Put in C2:
=ISNUMBER(MATCH(A2,B:B))
Copy down to the last row of data in col A
Apply autofilter on col C, filter for TRUE