sqlserver 2000/2005 Ambiguous column error错误解决办法

今天针对Sql server 2005的脚本在Sql server 2000上执行，发生了两个错误
Msg 209,Level 16,State 1,Procedure tbh_Forums_GetUnapprovedPosts,Line 13
Ambiguous column name 'AddedDate'.
Msg 209,Procedure tbh_Forums_GetThreadByID,Line 13
Ambiguous column name 'AddedDate'.

原来就是Forums表中和Post表中具有相同的列AddedDate，通过as 方式改写就可以解决了
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[tbh_Forums_GetThreadByID]') AND type in (N'P',N'PC'))
BEGIN
EXEC dbo.sp_executesql @statement = N'CREATE PROCEDURE [dbo].[tbh_Forums_GetThreadByID]
(
   @ThreadPostID  int
)
AS
SET NOCOUNT ON
  
SELECT tbh_Posts.PostID,tbh_Posts.AddedDate as AddedDate,tbh_Posts.AddedBy,tbh_Posts.AddedByIP,tbh_Posts.ForumID,tbh_Posts.ParentPostID,tbh_Posts.Title,tbh_Posts.Body,tbh_Posts.Approved,tbh_Posts.Closed,tbh_Posts.ViewCount,tbh_Posts.ReplyCount,tbh_Posts.LastPostDate,tbh_Posts.LastPostBy,
   tbh_Forums.Title AS ForumTitle
   FROM tbh_Posts INNER JOIN
      tbh_Forums ON tbh_Posts.ForumID = tbh_Forums.ForumID
   WHERE PostID = @ThreadPostID OR ParentPostID = @ThreadPostID
   ORDER BY AddedDate ASC'
END
GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
IF NOT EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[tbh_Forums_GetUnapprovedPosts]') AND type in (N'P',N'PC'))
BEGIN
EXEC dbo.sp_executesql @statement = N'CREATE PROCEDURE [dbo].[tbh_Forums_GetUnapprovedPosts]
AS
SET NOCOUNT ON

SELECT tbh_Posts.PostID,1)">tbh_Posts.AddedDate  as AddedDate,
   tbh_Forums.Title AS ForumTitle,CASE
                                    WHEN ParentPostID = 0 THEN 1
                                    ELSE 0
                                 END AS IsThreadPost
   FROM tbh_Posts INNER JOIN
      tbh_Forums ON tbh_Posts.ForumID = tbh_Forums.ForumID
   WHERE Approved = 0
   ORDER BY IsThreadPost DESC,AddedDate ASC'
END
GO

虽然这样解决了问题，这不应该是问题的真正原因，各位同学谁知道这个问题的真正原因？