declare
    dup_val_on_index  exception;
    pragma exception_init (dup_val_on_index  , -00001);
begin
    execute immediate 'ALTER TABLE AG_CONTAS_PAGAR ADD (ISSBASE NUMBER(12,2))';
    execute immediate 'ALTER TABLE AG_CONTAS_PAGAR ADD (ISSVALOR NUMBER(12,2))';
    exception when dup_val_on_index  then null;
end;