If you have two data sets

Set 1

1, 2

3, 4

Set 2

a, b

c, d

and you want to combine them to give something like

1, 2, a, b

3, 4, c, d

you need to find a way of linking set 1 and set 2. Otherwise who is to say that

1, 2, c, d

3, 4, a, b

is not correct?

So ... what is the link between your source data tables?