在Oracle中将此路径反转为z/y/x到x/y/z

Question

如何在SELECT查询中反转此路径:

z/y/x 

对于

x/y/z

where /是分隔符,在一行中可以有多个分隔符

ex: select (... z/y/x/w/v/u ...) reversed_path from ...

Answer 1

您可以通过连接还原的组件来获得结果,然后再次还原生成的字符串.只需确保剥离起始分隔符并将其放在另一侧:

SELECT '/' || REVERSE(LTRIM(SYS_CONNECT_BY_PATH(REVERSE(x), '/'), '/') AS reversed_path
...

Answer 2

最简单的方法可能是编写存储的pl / sql函数，但是可以单独使用SQL（Oracle）来完成。

这将分解子路径中的路径：

SQL> variable path varchar2(4000);
SQL> exec :path := 'a/b/c/def';

PL/SQL procedure successfully completed
SQL> SELECT regexp_substr(:path, '[^/]+', 1, ROWNUM) sub_path, ROWNUM rk
  2    FROM dual
  3  CONNECT BY LEVEL <= length(regexp_replace(:path, '[^/]', '')) + 1;

SUB_P RK
----- --
a      1
b      2
c      3
def    4

然后，我们使用重组反向路径sys_connect_by_path：

SQL> SELECT MAX(sys_connect_by_path(sub_path, '/')) reversed_path
  2    FROM (SELECT regexp_substr(:path, '[^/]+', 1, ROWNUM) sub_path,
  3                 ROWNUM rk
  4             FROM dual
  5           CONNECT BY LEVEL <= length(regexp_replace(:path, '[^/]', '')) + 1)
  6  CONNECT BY PRIOR rk = rk + 1
  7   START WITH rk = length(regexp_replace(:path, '[^/]', '')) + 1;

REVERSED_PATH
-------------
/def/c/b/a