Excel How to merge two columns into one from different sheets or separated columns

Question

When merging two columns into one, I occasionally run into issues. I have a solution, however, it doesn't quite address the issue. 

As I understand two columns have to be one by one:

A       B       C
==================
A       1       A
B       2       1
C       3       B
                2
                C
                3

To get the above solution in the C column I should use:

=INDEX($A$2:$B$9;ROUND(ROW(A1)/2;0);MOD(ROW();2)+1)

I, therefore, input data such as A1:B4 into the formula.

How can I do that if I only want to include columns A and D that have data instead of columns B and C? Alternatively, what if I had a column from sheet A and another from sheet B?

Answer 1

This equation is completely adjustable. Your two distinct columns can be on separate papers. Additionally, you can place the Result column wherever you choose.

=IF(ISEVEN(ROW())=FALSE;INDEX($A$4:$A$20;ROUND((ROWS($A$4:A4)/2);0));INDEX($B$6:$B$24;ROUND((ROWS($B$6:B6)/2);0)))