sql - 希望通过左外连接将数据添加到查询中而不重复

Question

我有一个数据库结构(下面的 ER 图)，它具有三级分层数据和第四级可选数据。

如果我编写一个查询来获取三个级别(级别 1 到级别 3)的非规范化数据，其中三个表中的示例数据如下所示:

查询时，这种数据布局非常简单，如下所示:

运行以下查询后，我得到以下输出(并且我尝试了各种组合，将 L1 集合组合到 L4 并将一个 L4 移出作为另一个查询，然后加入 L1 - L4 集合等)-这又符合预期。

SELECT        [Group].GroupId, [Group].GroupName, Category.CategoryId, Category.CategoryName, RLI.RLIId, RLI.RLIText, Comment.CommentId, Comment.CommentText, ManagementResponse.ManagementResponseId, 
                         ManagementResponse.ManagementResponseTest
FROM            Category INNER JOIN
                         [Group] ON Category.GroupId = [Group].GroupId INNER JOIN
                         RLI ON Category.CategoryId = RLI.CategoryId LEFT OUTER JOIN
                         ManagementResponse ON RLI.RLIId = ManagementResponse.RLIId LEFT OUTER JOIN
                         Comment ON RLI.RLIId = Comment.RLIId

但是，我需要以下格式的数据 - 这是我无法弄清楚如何获取的(当我通过左侧添加额外的 4 级数据时，我不希望 4 级数据重复外连接):

Answer 1

此查询将为您提供最终输出:

WITH CommentAndResponse AS (

SELECT Comment.CommentId,
         Comment.CommentText, 
         ManagementResponse.ManagementResponseId, 
         ManagementResponse.ManagementResponseTest,
    COALESCE(Comment.RLIId, ManagementResponse.RLIId) AS RLIId
 FROM (
    (SELECT Comment.CommentId, 
            Comment.CommentText,
            Comment.RLIId,
            ROW_NUMBER() OVER (PARTITION BY Comment.RLIId ORDER BY Comment.CommentId) AS CommentRowNumber
    FROM Comment) AS Comment
    FULL JOIN
    (SELECT  ManagementResponse.ManagementResponseId, 
            ManagementResponse.ManagementResponseTest,
            ManagementResponse.RLIId,
            ROW_NUMBER() OVER (PARTITION BY ManagementResponse.RLIId ORDER BY ManagementResponse.ManagementResponseId) AS ManagementResponseRowNumber   
    FROM ManagementResponse) AS ManagementResponse
    ON Comment.CommentRowNumber = ManagementResponse.ManagementResponseRowNumber AND Comment.RLIId = ManagementResponse.RLIId ) 
    )

SELECT          [Group].GroupId, [Group].GroupName, Category.CategoryId, Category.CategoryName, RLI.RLIId, RLI.RLIText, CommentAndResponse.CommentId, CommentAndResponse.CommentText, CommentAndResponse.ManagementResponseId, CommentAndResponse.ManagementResponseTest
FROM            [Category]
INNER JOIN      [Group] ON Category.GroupId = [Group].GroupId 
INNER JOIN      [RLI] ON Category.CategoryId = RLI.CategoryId 
LEFT OUTER JOIN [CommentAndResponse] ON RLI.RLIId = CommentAndResponse.RLIId