declare
  ja_existe  exception;
  pragma exception_init (ja_existe  , -00001);
begin
  execute immediate 'update ruta set INDRUTACENLADA=0 where INDRUTACENLADA is null';
  exception when ja_existe  then null;
end;
/
declare
begin
  execute immediate 'alter table ruta modify (INDRUTACENLADA not null)';
	exception when others  then null;
end;