Question

我在oracle DB中有2个表：项目和关系。

项目：

ID   
---
1
2
3
4
5
6
7

关系：

ID    parent  child 
--------------------
1     1       2
2     1       3
3     1       4
4     2       5
5     2       6
6     3       7

在关系表中，我存储了“项目”的层次结构（不要问为什么它存储在不同的表中）。

问题：

执行此查询时：

SELECT PARENT_ID, CHILD_ID, CONNECT_BY_ISLEAF, MAX(LEVEL) OVER () + 1 - LEVEL as rev_level
  FROM relationship
CONNECT BY PRIOR PARENT_ID = CHILD_ID
  START WITH CHILD_ID = 7;

我没有看到根父母，因为他作为一个孩子在这个表中不存在。

问题是如何将根父（ID = 1）添加到查询结果中，或者将其与“items”表连接并保留结果列（level和isleaf）。

Answer 1

请注意，您有两个方向 - 父母和孩子。选一个，不要混合两个。

  1  with x as (
  2     select 1 as id, 1 as parent, 2 as child from dual union all
  3     select 2,            1           , 3  from dual union all
  4     select 3            ,1,            4  from dual union all
  5     select 4            ,2,            5  from dual union all
  6     select 5            ,2,            6  from dual union all
  7     select 6            ,3,            7  from dual)
  8  select *
  9  from       x
 10  sTART WITH child = 7
 11* CONNECT BY PRIOR id= CHILD
SQL> /

        ID     PARENT      CHILD
---------- ---------- ----------
         6          3          7
         5          2          6
         4          2          5
         3          1          4
         2          1          3
         1          1          2

由prior id = child而不是prior parent = child

进行连接

Answer 2

CONNECT_BY_ISLEAF可以反过来工作（请参阅此链接http://technology.amis.nl/2009/11/14/oracle-11gr2-alternative-for-connect_by_isleaf-function-for-recursive-subquery-factoring-dedicated-to-anton/）

我假设您想要显示有关该项目的更多数据（如名称）如果是这种情况，只需左边加入项目表。

SELECT PARENT_ID AS PARENT_ID,CHILD_ID, i.name AS CHILD_NAME,
      CONNECT_BY_ISLEAF,
        MAX(LEVEL) OVER () + 1 - LEVEL AS rev_level
    FROM items i
  LEFT JOIN relationship r ON (i.id = r.CHILD_ID)
CONNECT BY  PRIOR PARENT_ID = CHILD_ID 
  START WITH CHILD_ID = 7
ORDER BY REV_LEVEL;

检查这个SQLfiddle：http://sqlfiddle.com/#!4/5c9fa/17 另外，请查看有关自下而上搜索（http://bitbach.wordpress.com/2010/10/18/implementing-bottom-up-path-traversal-for-hierarchical-tables/）

Oracle，选择关系

2 个答案: