Oracle: return a row even if select returns no rows

1 2 3 4 5 6 7 8 9 10

SELECT nvl(data_name, 'nothing') FROM (      SELECT data_name     FROM data_table     WHERE data_table.type = v_t_id       UNION ALL       SELECT NULL AS data_name     FROM dual   ) WHERE data_name is not null or ROWNUM = 1;