Hierarchical query

-- Oracle 

 

EMP 表里存在 父子关系 （ID & PARENT_ID）

 

ENAME      MGR       
---------- ----------
SCOTT      JONES     
ADAMS      SCOTT

 

SQL:

SELECT     ename
          ,PRIOR ename mgr
      FROM emp
     WHERE 1 = 1
       AND 'SCOTT' IN (ename, PRIOR ename)
START WITH mgr IS NULL
CONNECT BY PRIOR empno = mgr

 

在EMP TREE结构里 如何求 leaf node 的总个数？

SQL:

SELECT SUM (leaf_flag) leaf_cnt
  FROM (SELECT     (CASE
                       WHEN LEVEL >= LEAD (LEVEL, 1, LEVEL) OVER (ORDER BY 1)
                          THEN 1
                    END) leaf_flag
              FROM emp
        START WITH mgr IS NULL
        CONNECT BY PRIOR empno = mgr)

 

在TREE结构里怎么把 子节点的数据显示在夫节点？

WITH T AS 
	 (
		SELECT '1'MENU_ID,'0' P_MENU_ID,'A' NAME,0 AMT FROM DUAL UNION ALL
		SELECT '2'MENU_ID,'1' P_MENU_ID,'B' NAME,20 AMT FROM DUAL UNION ALL
		SELECT '3'MENU_ID,'2' P_MENU_ID,'C' NAME,30 AMT FROM DUAL UNION ALL
		SELECT '4'MENU_ID,'2' P_MENU_ID,'D' NAME,40 AMT FROM DUAL UNION ALL
		SELECT '5'MENU_ID,'1' P_MENU_ID,'E' NAME,50 AMT FROM DUAL UNION ALL
		SELECT '6'MENU_ID,'5' P_MENU_ID,'F' NAME,60 AMT FROM DUAL UNION ALL
		SELECT '7'MENU_ID,'6' P_MENU_ID,'G' NAME,70 AMT FROM DUAL
	 )

 

想要的结果？

 

NAME    AMT     AMT_CHILD
----    ---     ---------
A       0       270
B       20      90
C       30      30
D       40      40
E       50      180
F       60      130
G       70      70

 

SQL:

SELECT NAME
      ,amt
      , (SELECT     SUM (CASE
                            WHEN SYS_CONNECT_BY_PATH (menu_id, ',') || ',' LIKE '%,' || a.menu_id || ',%'
                               THEN amt
                         END)
               FROM t
         START WITH p_menu_id = 0
         CONNECT BY PRIOR menu_id = p_menu_id) amt_child
  FROM t a

 或者 更简洁

SELECT NAME
      ,amt
      , (SELECT     SUM (amt)
               FROM t
         START WITH menu_id = a.menu_id
         CONNECT BY PRIOR menu_id = p_menu_id) amt_child
  FROM t a