分层 SQL 查询不返回级别

发布于 2024-09-02 07:35:32 字数 476 浏览 4 评论 0原文

我有一个典型的 SQL Server 分层查询：

WITH bhp AS (
   SELECT name, 0 AS level
   FROM dbo.BhpNode
   WHERE parent_id IS NULL
   UNION ALL
   SELECT a.name, level + 1
   FROM dbo.BhpNode a
   INNER JOIN dbo.BhpNode b
      ON b.bhp_node_id = a.parent_id )
  SELECT * FROM bhp

这似乎与我在网上找到的分层查询的各种示例相匹配，但由于某种原因它产生了此错误：

消息 207，第 16 级，状态 1，第 12 行
列名“level”无效。

我确信我错过了一些明显的东西，但我已经盯着它看太久了，看不到它。知道我哪里出错了吗？

原文

I have a typical SQL Server hierarchical query:

WITH bhp AS (
   SELECT name, 0 AS level
   FROM dbo.BhpNode
   WHERE parent_id IS NULL
   UNION ALL
   SELECT a.name, level + 1
   FROM dbo.BhpNode a
   INNER JOIN dbo.BhpNode b
      ON b.bhp_node_id = a.parent_id )
  SELECT * FROM bhp

This seems to match the various examples of hierarchical queries I've found around the web, but for some reason it's producting this error:

Msg 207, Level 16, State 1, Line 12
Invalid column name 'level'.

I'm sure I'm missing something obvious, but I've stared at it too long to see it. Any idea where I'm going wrong?

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凝望流年 2024-09-09 07:35:32

您的查询不是递归的 - 您必须从递归 CTE 的第二部分内的 bhp 中进行选择。试试这个：

WITH bhp AS (
   SELECT *, 0 AS [level]
   FROM dbo.BhpNode
   WHERE parent_id IS NULL
   UNION ALL
   SELECT b.*, [level] + 1
   FROM bhp a
   INNER JOIN dbo.BhpNode b
   ON a.bhp_node_id = b.parent_id)
SELECT * FROM bhp

Your query isn't recursive - you have to select from bhp inside the second part of the recursive CTE. Try this instead:

WITH bhp AS (
   SELECT *, 0 AS [level]
   FROM dbo.BhpNode
   WHERE parent_id IS NULL
   UNION ALL
   SELECT b.*, [level] + 1
   FROM bhp a
   INNER JOIN dbo.BhpNode b
   ON a.bhp_node_id = b.parent_id)
SELECT * FROM bhp

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