Sql 如何在一个表上查找父子关系的所有子项

如何找到文件夹下的所有子项？就像在资源管理器中，你有一个文件夹在neeth下，你有文件夹+文件夹等

我想找到文件夹2下的所有文件夹

我正在使用oracledb

Folder 1
| |
| Folder 2
| |  |
| |  Folder 3
| |  |  |
| |  |  Folder 7
| |  |  |
| |  |  Folder 8
| |  |
| |  Folder 4
| |
| Folder 5
| |
| Folder 6 
|
Folder 10

这个查询为我提供了父层次结构

SELECT AL_ITEM_ID, AL_FATHER_ID, AL_DESCRIPTION
FROM ALL_LISTS
CONNECT BY AL_ITEM_ID = PRIOR AL_FATHER_ID
start with AL_DESCRIPTION = 'Folder 7'

---

我认为这会奏效：

Select
    al_item_id, 
    al_father_id,
    al_description
From 
    all_lists
Connect By 
    Prior al_item_id = al_father_id
Start With
    al_description = 'Folder 2'
Where
    Level > 1

如果不是，这几乎可以肯定，这取决于where是在connect之前还是之后通过以下方式进行计算：

Select
    al_item_id,
    al_father_id,
    al_description
From (
    Select
        al_item_id, 
        al_father_id,
        al_description,
        level as lvl
    From 
        all_lists
    Connect By 
        Prior al_item_id = al_father_id
    Start With
        al_description = 'Folder 2'
    ) x
Where
    lvl > 1

---

只需将Previor放在另一边

通过Previor al_item_id=al_father_id连接

，然后

从更高层次的东西开始。好的工作。如果我从文件夹2开始，我将如何不在列表中显示文件夹2？现在我看到文件夹2，3，7，8。如何获取文件夹3、7、8