declare
    object_exists exception;
    pragma exception_init (object_exists , -00955);
begin
	execute immediate 'ALTER TABLE CAJA_DIVERSOS_PAGO
					   ADD CONSTRAINT FK_CAJA_DIVERSOS_PAGO_OCD FOREIGN KEY (OCD_ID)
					   REFERENCES OCD (OCD_ID)';
    exception when object_exists then null;
end;