declare
    object_exists exception;
    pragma exception_init (object_exists , -01430);
begin
	execute immediate 'ALTER TABLE ESTACION add INDSTOCKCENTRAL NUMBER(1)';
	execute immediate 'ALTER TABLE ESTACION_IMPRESORA add ESTACIONCENTRAL_ID NUMBER(7)';
	execute immediate 'ALTER TABLE FOLIO_PREIMPRESO add CONFIRMANDO NUMBER(7)';
	exception when object_exists then null;
end;