declare
    object_exists exception;
    pragma exception_init (object_exists , -01430);
begin
	execute immediate 'ALTER TABLE CATEGORIA_BLOQ_IMPPOSTERIOR ADD (ACTIVO NUMBER(1) DEFAULT 0 NOT NULL)';	
	execute immediate 'ALTER TABLE CATEGORIA_BLOQ_IMPPOSTERIOR ADD (FECMODIF DATE)';	
	execute immediate 'ALTER TABLE CATEGORIA_BLOQ_IMPPOSTERIOR ADD (USUARIO_ID NUMBER(7))';
    exception when object_exists then null;
end;