How to copy one field to another in a Table in AX

static void CopyOneFieldToAnotherField(Args _args)
{
    TableA  t1; // Declare your Table name here.
    ;
    ttsbegin;
    while select forupdate t1 where t1.Num == t1.num // Num is the 1st field name of your table.
    {
         t1.SerialNumberFormat = t1.num;  // SerialNumberFormat is the 2nd field name of your table.
         t1.Num = ""; // If you don't want to delete from 1st field after copying the data.
         t1.update();
    }
    ttscommit;
}