Updating internal table

Hi Experts,

Please help me,

Here i have final internal table with all my fields except one description field.

I need to fetch that from another table and i have to update correspondingly.

Can any one tell me how to do that.

Right now my data as below:

Materialno description deptno section

101 1 xyz

102 2 pqr

Now i don't have description field in my final internal table. now i have to pick up from another table and i have to update correspondingly,

Thanks and regards,