Filling down a VLOOKUP formula without changing the range

Question

I am comparing values in a row in one sheet to values in another row in another sheet. The following formula and works:

=IFERROR(VLOOKUP(A1,Sheet1!A1:A19240,1,FALSE),"No Match")

My problem is when I fill down the formula, it increments A1 correctly but also increments the (A1:A19240), so half way down I have narrowed the search field.

How can I apply this formula to a column?

Answer 1

Change A1:A19240 to A$1:A$19240, i.e. apply:

=IFERROR(VLOOKUP(A1,Sheet1!A$1:A$19240,1,FALSE),"No Match")

This is called using absolute references.