declare
    column_exists exception;
    pragma exception_init (column_exists , -01430);
begin
    execute immediate 'ALTER TABLE EMPRESA ADD INDEMITECANCBPETROCAORIGDEST NUMBER(1,0) DEFAULT 1';
    exception when column_exists then null;
end;
/
declare
    object_exists exception;
    pragma exception_init (object_exists , -00001);
begin
	execute immediate 'UPDATE EMPRESA SET FECMODIF = SYSDATE';
	exception when object_exists then null;
end;