If the structure of both the file are same, You can try Union.
I forgot to mention, I have tried to use Union as well.
However, most of the columns are different between the two files, only a few are identical, the column "Days" is one of them. Therefore, Union still not work for me.
Thank you for the reply.
You can easily do this with cross Join & Pivot data
Still need help, let me know and send sample workbook
I found the solution. It turns out that IFNULL is easier for me to use.