甲骨文9i中得到给定子树的最高成员
-
22-07-2019 - |
题
我在Oracle 9i数据库表的父子关系
像:
parent | child
1 | 2
2 | 3
2 | 4
null | 1
1 | 8
我需要从一个给定的孩子得到绝对的父母。 说,我的孩子4,它给我的父:1
我已经看了BY连接,但我不能找到解决方案。
解决方案
您可以使用CONNECT BY查询来建立家长的名单,然后进行过滤:
SQL> WITH tree AS (
2 SELECT 1 parent_id, 2 child_id FROM DUAL
3 UNION ALL SELECT 2 , 3 FROM DUAL
4 UNION ALL SELECT 2 , 4 FROM DUAL
5 UNION ALL SELECT null, 1 FROM DUAL
6 UNION ALL SELECT 1 , 8 FROM DUAL
7 )
8 SELECT child_id
9 FROM (SELECT *
10 FROM tree
11 CONNECT BY PRIOR parent_id = child_id
12 START WITH child_id = 4)
13 WHERE parent_id IS NULL;
CHILD_ID
----------
1
其他提示
SELECT parent
FROM (
SELECT parent
FROM (
SELECT parent, level AS l
FROM mytable
START WITH
child = 4
CONNECT BY
child = PRIOR parent
)
ORDER BY
l DESC
)
WHERE rownum = 1
这会给你NULL
作为绝对父。
如果你想1
,更换parent
child
:
SELECT child
FROM (
SELECT child
FROM (
SELECT child, level AS l
FROM mytable
START WITH
child = 4
CONNECT BY
child = PRIOR parent
)
ORDER BY
l DESC
)
WHERE rownum = 1
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