MySQL相關子查詢：子查詢無法從外部查詢中查找表？

Question

自從我使用核心子查詢以來，它已經有一段時間了，我不確定我是否正在做這件事。在我的子查詢的最後一行中，我試圖從外表獲得node.id。當我嘗試執行查詢，我得到

錯誤代碼：1054未知列 「node.id」在「where子句」）

select node.id, node.title, depthLookup.depth 
from posts node, (
    select count(parent.title) as depth 
    from posts parent, posts children 
    where children.lft > parent.lft 
    and children.rgt < parent.rgt 
    and children.id = node.id 
    order by parent.lft 
) as depthLookup; 

Answer 1

看來你只需要移動你表達從「從」子句字段列表

select node.id, node.title, 
(
    select count(parent.title) as depth 
    from posts parent, posts children 
    where children.lft > parent.lft 
    and children.rgt < parent.rgt 
    and children.id = node.id 
    order by parent.lft 
) as depthLookup 
from posts node; 

或者使用單值表所示：

select node.id, node.title, depthLookup.depth 
from posts node, 
(
    select count(parent.title) as depth 
    from posts parent, posts children 
    where children.lft > parent.lft 
    and children.rgt < parent.rgt 
    and children.id = node.id 
    order by parent.lft 
) as depthLookup;