Returning a value if data is in a large list

[Guest]

I think you use a IF function but I am not sure.

I have two large lists of numbers. The lists are in columns A and C with
columns B and D blank. In B, I want to insert an "X" if the number in column
A next to it is somewhere in column C. I tried =IF(A2=C:C,"X","") and
=IF(A2=C2;C1000,"X","") but they do not work. Is there a way I can do this?

 

[Dave Peterson]

One way:
=IF(COUNTIF(C:C,A1)>0,"x","")

Another way:
=IF(ISNUMBER(MATCH(A1,C:C,0)),"x","")

I like the second way. It'll be faster for larger lists in column C.

 

[gazornenplat]

=IF(ISNA(MATCH(B4,D48)),"","X")

is, I think, what you want.

Gaz