Question

使用CONNECT BY PRIOR在Oracle中存在分层查询。大家都知道，如何按父母选择孩子，但我需要按孩子选择父母。

这是我的表：

ID  PID     NAME            TYPE
1   null    EARTH           PLANET
2   1       USA             COUNTRY
3   2       CALIFORNIA      STATE
4   3       Los_Angeles     CITY
5   3       San_Francisco   CITY
6   3       San_Diego       CITY

在我的应用程序中，我有San_Diego的ID，我需要知道，San_Diego在哪个国家/地区？我需要用我的查询获得USA（TYPE = COUNTRY）吗？如何用oracle层次结构选择它？

Answer 1

层次结构意味着表格的一行是＆＃34;父级＆＃34;，另一个是 - ＆＃34;孩子＆＃34;。 PRIOR用于显示谁是谁。条款CONNECT BY PRIOR EMPNO = MGR表示如果两行具有相同的值，但是列EMPNO中的一行，而第二行 - 在列MGR中，则第二行是＆＃34; parent＆＃34;首先是一个孩子＆＃34;。所以，查询

SELECT EMPNO,ENAME,MGR,LEVEL
FROM TMP_PCH
CONNECT BY PRIOR EMPNO = MGR
START WITH MGR = 'John'

返回John（和John本身）的所有下属，并查询

SELECT EMPNO,ENAME,MGR,LEVEL
FROM TMP_PCH
CONNECT BY PRIOR MGR = EMPNO
START WITH MGR = 'John'

返回John（和John本人）的所有老板。

Answer 2

您需要为connect by创建正确的条件，然后从叶子'圣地亚哥'开始：

select name 
  from (
    select * from test 
      connect by id = prior pid
      start with name='San_Diego')
  where type='COUNTRY'

SQL Fiddle demo

Answer 3

SELECT * FROM places_table
WHERE type = 'COUNTRY'
START WITH id = 6 -- San Diego
CONNECT BY PRIOR pid = id;

Answer 4

没有区别，你只需要在父方面使用PRIOR。例如，获取圣地亚哥市的树：

WITH your_table AS (  
  SELECT 1 id, NULL pid, 'EARTH' name, 'PLANET' type FROM dual
  UNION
  SELECT 2 id, 1 pid, 'USA' name, 'COUNTRY' type FROM dual
  UNION
  SELECT 3 id, 2 pid, 'CALIFORNIA' name, 'STATE' type FROM dual
  UNION 
  SELECT 4 id, 3 pid, 'Los_Angeles' name, 'CITY' type FROM dual
  UNION 
  SELECT 5 id, 3 pid, 'San_Francisco' name, 'CITY' type FROM dual
  UNION
  SELECT 6 id, 3 pid, 'San_Diego' name, 'CITY' type FROM dual
)
SELECT id, name, level
FROM your_table
CONNECT BY id = PRIOR pid
START WITH id = 6

如果您只想获得该国家/地区，则可以按级别进行过滤：

WITH your_table AS (  
  SELECT 1 id, NULL pid, 'EARTH' name, 'PLANET' type FROM dual
  UNION
  SELECT 2 id, 1 pid, 'USA' name, 'COUNTRY' type FROM dual
  UNION
  SELECT 3 id, 2 pid, 'CALIFORNIA' name, 'STATE' type FROM dual
  UNION 
  SELECT 4 id, 3 pid, 'Los_Angeles' name, 'CITY' type FROM dual
  UNION 
  SELECT 5 id, 3 pid, 'San_Francisco' name, 'CITY' type FROM dual
  UNION
  SELECT 6 id, 3 pid, 'San_Diego' name, 'CITY' type FROM dual
)
SELECT id, name, level
FROM your_table
WHERE LEVEL = 3
CONNECT BY id = PRIOR pid
START WITH id = 6

在Oracle数据库

4 个答案: