如何使用SQL在数据库中检测具有嵌套关系的父级? [英] How can you detect a parent with a nested relationship in a database using SQL?

问题描述

我正在使用Firebird 2.1.表名称为Folders，其字段为:

I'm using Firebird 2.1. There is a table name Folders, with the fields:

• 文件夹ID
• ParentFolderID
• FolderName

ParentFolderID是根文件夹，则为-1-否则包含父文件夹的ID.

ParentFolderID is -1 if it's the root folder -- otherwise it contains the parent folder's ID.

如何找到低级别节点的所有父节点(直到根文件夹)?

How can I find all parents (up to the root folder) of a low level node?

我需要递归查询吗? ( Firebird支持它们)

Do I need a recursive query? (Firebird supports them)

推荐答案

类似以下内容:

WITH RECURSIVE hierarchy (folderid, ParentFolderId, FolderName) as (
   SELECT folderid, ParentFolderId, FolderName
   FROM folders
   WHERE ParentFolderID = -1

   UNION ALL

   SELECT folderid, ParentFolderId, FolderName
   FROM folders f
     JOIN hierarchy p ON p.folderID = f.parentFolderID
)
SELECT *
FROM hierarchy

编辑:以下查询将使层次结构向上"移动，找到给定文件夹的所有父项.

Edit: the following query will walk the hierarchy "up", finding all parents of a given folder.

WITH RECURSIVE hierarchy (folderid, ParentFolderId, FolderName) as (
   SELECT folderid, ParentFolderId, FolderName
   FROM folders
   WHERE folderid = 42

   UNION ALL

   SELECT folderid, ParentFolderId, FolderName
   FROM folders f
     JOIN hierarchy p ON p.parentFolderID = f.folderID
)
SELECT *
FROM hierarchy

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