Walk parent/child tree with recursive CTE?

问题:

I am stuck with a cte, I want a query where in first parent is null. and child of pervious parent, will be the parent of next, and so on.

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

The above mentioned is my query. Please help me to iterate through last child.

The output I have is:

 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

The Output I desire is:

 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

回答1:

Without seeing your underlying tables, I can't test any suggestions. But, see what happens if you swtich parent and child in the outer query:

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

回答2:

For the output you specify, the rows in your CTE would need to be ranked and then you just filter for rows ranked 1 in each iteration.

WITH RESULT (ROW_RANK, PARENT,CHILD,TNAME,[LEVEL])
AS
(
--anchor
 SELECT RANK() OVER (ORDER BY E.M_GENERAL_KEY), 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 RANK() OVER (ORDER BY E.M_GENERAL_KEY), E.PARENT_GENERAL_KEY,E.M_GENERAL_KEY,E.NAME, D.[LEVEL] +1 
 FROM RPT_SYN_M_GENERAL AS E
 INNER JOIN RESULT AS D  
 ON E.PARENT_GENERAL_KEY=D.CHILD AND ROW_RANK = 1
)
SELECT PARENT,CHILD,TNAME,LEVEL FROM RESULT as d
WHERE ROW_RANK = 1
order by PARENT,CHILD