SQL Server中的ORACLE Con​​nect by子句等效 [英] ORACLE Connect by clause equivalent in SQL Server

问题描述

在SQL Server中是否有与Oracle的CONNECT BY等效的子句.使用parentId字段构建类别树的要求.

Is there a equivalent clause to CONNECT BY of Oracle in SQL Server. The requirement to build a category tree using a parentId field.

推荐答案

与SQL Server 2005+等效的Oracle CONNECT BY层次查询语法是使用递归CTE. SQL Server 2008添加了 HierarchyID .这是递归CTE的示例:

The SQL Server 2005+ equivalent of Oracle's CONNECT BY hierarchical query syntax is to use a recursive CTE. SQL Server 2008 added HierarchyID. Here's an example of a recursive CTE:

WITH EmployeeHierarchy (EmployeeID, LastName, FirstName, ReportsTo, HierarchyLevel) AS (
   SELECT EmployeeID,
          LastName,
          FirstName,
          ReportsTo,
          1 as HierarchyLevel
     FROM Employees
    WHERE ReportsTo IS NULL
   UNION ALL
   -- Recursive step
   SELECT e.EmployeeID,
          e.LastName,
          e.FirstName,
          e.ReportsTo,
          eh.HierarchyLevel + 1 AS HierarchyLevel
     FROM Employees e
     JOIN EmployeeHierarchy eh ON e.ReportsTo = eh.EmployeeID)
  SELECT *
    FROM EmployeeHierarchy
ORDER BY HierarchyLevel, LastName, FirstName 

谷歌搜索分层CTE"和/或递归CTE"将产生大量结果.我从 4GuysFromRolla.com 中获取了示例查询.

Googling "hierarchical CTE" and/or "recursive CTE" will turn up numerous results. I took the example query from the 4GuysFromRolla.com.

递归CTE现在是ANSI标准-据我所知，直到Oracle 11g才支持该语法.

Recursive CTEs are now ANSI standard - the syntax wasn't supported until Oracle 11g as I understand.

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