如有下面的表结构AAAA，用一个字段prev_id表示记录的先后顺序，要对其排序，需要用的递归函数
| ID | PREV_ID | CONT |
| 99 | a | |
| 23 | 54 | d |
| 21 | 23 | e |
| 54 | 33 | c |
| 33 | 99 | b |
| 32 | 45 | g |
| 45 | 21 | f |
如：
create or replace function sequen(cid number)
return number is
pid number(2);
begin
select prev_id into pid from aaaa where id=cid;
if pid is null then return 1;
else return sequen(pid)+1; --递归调用自己
end if;
end;
查询语句 select sequen(id) sq, t.* from AAAA t order by sq
结果：
| SQ | ID | PREV_ID | CONT |
| 1 | 99 | a | |
| 2 | 33 | 99 | b |
| 3 | 54 | 33 | c |
| 4 | 23 | 54 | d |
| 5 | 21 | 23 | e |
| 6 | 45 | 21 | f |
| 7 | 32 | 45 | g |