How to print columns one after the other in bash?

Question

Is there any better methods to print two or more columns into one column, for example

input.file

AAA    111
BBB    222
CCC    333

o

Answer 1

Expects tab as delimiter:

$ cat <(cut -f 1 asd) <(cut -f 2 asd)
AAA
BBB
CCC
111
222
333