Question

我有下表：

CREATE TABLE Z_BOM2 (A  VARCHAR2(4 CHAR), B  VARCHAR2(4 CHAR));
Insert into Z_BOM2 (A, B) Values ('A', 'B');
Insert into Z_BOM2 (A, B) Values ('A', 'C');
Insert into Z_BOM2 (A, B) Values ('C', 'D');
Insert into Z_BOM2 (A, B) Values ('C', 'F');
Insert into Z_BOM2 (A, B) Values ('D', 'E');
COMMIT;



SELECT * FROM Z_BOM2;
A   B
A   C
C   D
C   F
D   E

A是父母，B是孩子。

我想在查询中输入子值'E'和'F'，并且只获得那些对于这两者都应该是'A'的顶级父级。这是我正在使用的查询：

select SYS_CONNECT_BY_PATH (a,'/') as path, a, b, level, CONNECT_BY_ISLEAF AS leaf, CONNECT_BY_ROOT b top_level
  from Z_BOM2
  connect by prior a = b
  start with b IN ('E', 'F');

返回以下内容：

/D  D   E   1   0   E
/D/C    C   D   2   0   E
/D/C/A  A   C   3   1   E
/C  C   F   1   0   F
/C/A    A   C   2   1   F

为什么不返回正确的顶级父级？

Answer 1

来自CONNECT_BY_ROOT的顶级家长取决于您的起始条件以及您走树的方向。你向后走树，所以根本就是这样。这真的是你的起始条件。

您实际上已经拥有了所需的信息，但在A列中，您可以获得叶节点：

select SYS_CONNECT_BY_PATH (a,'/') as path, a, b, level,
  CONNECT_BY_ISLEAF AS leaf, CONNECT_BY_ROOT b top_level
from Z_BOM2
where CONNECT_BY_ISLEAF = 1
connect by prior a = b
start with b IN ('E', 'F');

PATH                 A    B         LEVEL       LEAF TOP_LEVEL
-------------------- ---- ---- ---------- ---------- ---------
/D/C/A               A    C             3          1 E         
/C/A                 A    C             2          1 F

要仅获取您感兴趣的顶级值，请仅在选择列表中包含列A。

SQL Fiddle demo

这适用于您在评论中添加的结构; SQL Fiddle。 C得B; J获得A; D得到A和B：

select CONNECT_BY_ROOT b query_val, a as top_level
from Z_BOM2
where CONNECT_BY_ISLEAF = 1
connect by prior a = b
start with b IN ('C', 'D', 'J');

QUERY_VAL TOP_LEVEL
--------- ---------
C         B         
D         A         
D         B         
J         A

Answer 2

在LEVEL上制作一个WHERE条件

WITH t AS
   (select SYS_CONNECT_BY_PATH (a,'/') as path, a, b, level as LEV,
      CONNECT_BY_ISLEAF AS leaf, CONNECT_BY_ROOT b top_level
   from Z_BOM2
   connect by prior a = b
   start with b IN ('E', 'F'))
SELECT *
FROM t
WHERE LEV = 1;

使用Connect by获取树中的顶级部件

2 个答案: