I have met some problem with merging two columns to one. I have some solution but not exactly fits to my problem (found here: Excel: Merge two columns into one column with alternating values)
As I understand two columns has 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 C column I should use:
=INDEX($A$2:$B$9;ROUND(ROW(A1)/2;0);MOD(ROW();2)+1)
So in the formula I'm using data like A1:B4.
How to do it if I will have columns with data A and D and I dont want to include columns B and C? Or for instance I will have one column from sheet_A and second column from sheet_B?


