sql - 使用递归 CTE 遍历父/子树？

Question

我被 cte 困住了， 我想要一个查询，其中第一个父项为空。 和上一个 parent 的 child ，将成为下一个 parent 的 parent ，依此类推。

WITH RESULT (PARENT,CHILD,TNAME,LEVEL)
AS
(
--anchor
 SELECT E.PARENT_GENERAL_KEY,E.M_GENERAL_KEY,E.NAME ,0 AS LEVEL
  FROM RPT_SYN_M_GENERAL AS E 
 WHERE E.PARENT_GENERAL_KEY IS NULL
 UNION ALL
 --outer
 SELECT e.PARENT_GENERAL_KEY,E.M_GENERAL_KEY,e.NAME ,LEVEL +1
 FROM RPT_SYN_M_GENERAL AS E
 INNER JOIN RESULT AS D  
 ON E.PARENT_GENERAL_KEY=D.CHILD 
)
SELECT PARENT,CHILD,TNAME,LEVEL FROM RESULT as d
order by PARENT,CHILD

以上是我的查询。 请帮我遍历最后一个 child 。

我的输出是:

 PARENT CHILD   TNAME               LEVEL
  NULL  0       ACCOUNT_MASTER        0
   0    1       LIABILITIES           1
   0    2       ASSETS                1
   0    3       INCOME                1
   0    4       EXPENSE               1
   0    15003   POLISHED DIAMOND      1
   0    15004   DEMO                  1
   0    15005   DEMO ( FACTORY        1
   1    238     CAPITAL A/C.          2
   1    1067    PROVISION             2
   1    1284    SECURED LOANS         2 
   1    2968    UNSECURED LOANS       2
   1    3535    SHARE HOLDERS         2
   2    484     FIXED ASSETS A/C      2
   2    3301    INVESTMENTS           2
   2    4858    CURRENT ASSETS        2
   2    4859    LOANS ADVANCES        2
   3    867     OTHER INCOME          2
   3    1246    SALES                 2

我想要的输出是:

 PARENT      CHILD  TNAME             LEVEL
   null      0                          0
    0        1                          1 
    1        238                        2
   238       982                        3
   982       26                         4
   982       894                        4        
   982       1321                       4
   238       7757                       3
   7757      7521                       4

Answer 1

在没有看到您的基础表的情况下，我无法测试任何建议。但是，如果您在外部查询中切换父项和子项，看看会发生什么:

WITH RESULT (PARENT,CHILD,TNAME,LEVEL)
AS
(
--anchor
 SELECT E.PARENT_GENERAL_KEY,E.M_GENERAL_KEY,E.NAME ,0 AS LEVEL
  FROM RPT_SYN_M_GENERAL AS E 
 WHERE E.PARENT_GENERAL_KEY IS NULL
 UNION ALL
 --outer
 SELECT D.CHILD,D.PARENT,e.NAME ,LEVEL +1 --switched parent/child
 FROM RPT_SYN_M_GENERAL AS E
 INNER JOIN RESULT AS D  
 ON E.PARENT_GENERAL_KEY=D.CHILD 
WHERE LEVEL<100
)
SELECT PARENT,CHILD,TNAME,LEVEL FROM RESULT as d
order by PARENT,CHILD