copy of internal tables

hi all,

how we can copy internal table itab1 into internal table itab2

itab1 having 2 fileds and itab2 having 3 fields.

now, i want an internal tbale who is having 5 filds i.e 2 fields of itab1 and 3 fields of itab2

so, we clubed these fileds into an internal table.