merging internal tables.

Hi,

I have an internal table it1 with field f1

it-f1.The value gets filled in one loop.

it-f1 = 10.

I have another internal table it1 with fields f1 and f2.

say it1-f2 = 20 , it1-f3=30.

I want everything in one internal table in the format

it1-f1= 10

it1-f2 =20

it1-f3 =30

How to do it...it1 consists of the field declaration f1 also...

Thanks.