潇湘夜雨

reverse() reverses a single byte string but it does not work well with multi-byte characters

SQL> select reverse('abc') from dual;
REVERS
------
cba

SQL> exec :mystr := '国中cba';
1 SELECT max(replace(SYS_CONNECT_BY_PATH (c, '/'), '/')) keep (dense_rank last order by level)
2 FROM (SELECT LEVEL lvl, SUBSTR (:mystr, LEVEL, 1) c
3 FROM (SELECT LENGTH (:mystr) len
4 FROM DUAL) x
5 CONNECT BY LEVEL <= x.len
6 ORDER BY 1 DESC)
7* CONNECT BY PRIOR lvl = lvl + 1

MAX(REPLACE(SYS_CONNECT_BY_PATH(C,'/'),'/'))KEEP(DENSE_RANKLASTORDERBYLEVEL)
----------------------------------------------------------------------------
abc中国