内部联接返回冗余数据而不是预期数据

Question

我有以下查询-

 SELECT CP.PostID,CP.SectionID                              
     FROM NewsLetter NW  
     inner Join MapNewsletterPosts as MM on NW.ID = MM.ID        
     inner join CSPosts as CP with (nolock) on MM.PostID = CP.PostID       
     inner join PostStatus PS on PS.Postid=CP.PostId      
     WHERE  
     NW.NewsletterDate = '2015-07-06' 
     and CP.IsApproved =1                                           
     ANd PS.StatusId =7      
     AND CP.SectionID NOT IN (92,227)        
     AND NW.SectionID = 95
     ORDER BY MM.Newslettersortorder 

上面的查询返回正确的结果如下图-

现在，当我在上述查询中再添加一个连接时 -

SELECT CP.PostID,CP.SectionID                                
     FROM NewsLetter NW    
     inner Join MapNewsletterPosts as MM on NW.ID = MM.ID          
     inner join CSPosts as CP with (nolock) on MM.PostID = CP.PostID         
     inner join PostStatus PS on PS.Postid=CP.PostId      
     INNER JOIN NewsletterDetails ND ON ND.NewsletterDate = NW.NewsletterDate AND ND.IncludeInArticles=1 <<--added extra JOIN   
     WHERE    
     NW.NewsletterDate = '2015-07-06'   
     and CP.IsApproved =1                                             
     ANd PS.StatusId =7        
     AND CP.SectionID NOT IN (92,227)          
     AND NW.SectionID = 95  
     ORDER BY MM.Newslettersortorder 

导致数据冗余如下图-

我需要在查询中进行哪些更改才能返回正确的结果 [不同]。 提前谢谢...！！

Answer 1

您可以用EXISTS() 替换额外的连接：

 SELECT CP.PostID,CP.SectionID                              
 FROM NewsLetter NW  
 inner Join MapNewsletterPosts as MM on NW.ID = MM.ID        
 inner join CSPosts as CP with (nolock) on MM.PostID = CP.PostID       
 inner join PostStatus PS on PS.Postid=CP.PostId      
 WHERE EXISTS(SELECT 1 FROM NewsletterDetails nd
              WHERE ND.NewsletterDate = NW.NewsletterDate AND ND.IncludeInArticles=1)
      AND NW.NewsletterDate = '2015-07-06' 
      and CP.IsApproved =1                                           
      ANd PS.StatusId =7      
      AND CP.SectionID NOT IN (92,227)        
      AND NW.SectionID = 95
 ORDER BY MM.Newslettersortorder 

发生这种情况是因为额外表中有超过 1 行具有相同的 NewsletterDate，存在将消除这种情况，您将不再需要使用 DISTINCT 或 GROUP BY。

编辑：如果您只想要那些不存在带有IncludeInArticles=0 的记录的记录，那么使用这个：

 SELECT CP.PostID,CP.SectionID                              
 FROM NewsLetter NW  
 inner Join MapNewsletterPosts as MM on NW.ID = MM.ID        
 inner join CSPosts as CP with (nolock) on MM.PostID = CP.PostID       
 inner join PostStatus PS on PS.Postid=CP.PostId      
 WHERE NOT EXISTS(SELECT 1 FROM NewsletterDetails nd
                  WHERE ND.NewsletterDate = NW.NewsletterDate AND ND.IncludeInArticles=0)
      AND NW.NewsletterDate = '2015-07-06' 
      and CP.IsApproved =1                                           
      ANd PS.StatusId =7      
      AND CP.SectionID NOT IN (92,227)        
      AND NW.SectionID = 95
 ORDER BY MM.Newslettersortorder 

编辑：很难理解你到底想要什么！我猜你想要有 IncludeInArticles = 1 而没有 IncludeInArticles=0 的记录？现在这是唯一的选择：

 SELECT CP.PostID,CP.SectionID                              
 FROM NewsLetter NW  
 inner Join MapNewsletterPosts as MM on NW.ID = MM.ID        
 inner join CSPosts as CP with (nolock) on MM.PostID = CP.PostID       
 inner join PostStatus PS on PS.Postid=CP.PostId      
 WHERE EXISTS(SELECT 1 FROM NewsletterDetails nd
              WHERE ND.NewsletterDate = NW.NewsletterDate AND ND.IncludeInArticles=1)
   AND NOT EXISTS(SELECT 1 FROM NewsletterDetails nd
                  WHERE ND.NewsletterDate = NW.NewsletterDate AND ND.IncludeInArticles=0)
      AND NW.NewsletterDate = '2015-07-06' 
      and CP.IsApproved =1                                           
      ANd PS.StatusId =7      
      AND CP.SectionID NOT IN (92,227)        
      AND NW.SectionID = 95
 ORDER BY MM.Newslettersortorder 

Answer 2

您可以将ON 条件替换为ND.PostId =CP.PostID

试试这个 -

SELECT CP.PostID,CP.SectionID                                
     FROM NewsLetter NW    
     inner Join MapNewsletterPosts as MM on NW.ID = MM.ID          
     inner join CSPosts as CP with (nolock) on MM.PostID = CP.PostID         
     inner join PostStatus PS on PS.Postid=CP.PostId      
     INNER JOIN NewsletterDetails ND ON ND.PostId =CP.PostID AND ND.IncludeInArticles=1    
     WHERE    
     NW.NewsletterDate = '2015-07-06'   
     and CP.IsApproved =1                                             
     ANd PS.StatusId =7        
     AND CP.SectionID NOT IN (92,227)          
     AND NW.SectionID = 95  
     ORDER BY MM.Newslettersortorder 

Answer 3

最终的内部连接将有每个 PostID 的多行数据。

返回第一组结果的最简单方法是将 distinct 修饰符添加到选择：

SELECT DISTINCT CP.PostID,CP.SectionID

Answer 4

发生这种情况的原因是 NewsLetterDetails 中有多行数据。尝试将此表中的一个字段拉入您的查询中，以了解我的意思。

 SELECT 
     CP.PostID
     ,CP.SectionID 
     ,ND.*                            
 FROM NewsLetter NW    
 INNER JOIN MapNewsletterPosts as MM 
     ON NW.ID = MM.ID          
 INNER JOIN CSPosts as CP with (nolock) 
     ON MM.PostID = CP.PostID         
 INNER JOIN PostStatus PS 
     ON PS.Postid=CP.PostId      
 INNER JOIN NewsletterDetails ND 
     ON ND.NewsletterDate = NW.NewsletterDate 
     AND ND.IncludeInArticles=1    
 WHERE NW.NewsletterDate = '2015-07-06'   
     AND CP.IsApproved =1                                             
     AND PS.StatusId =7        
     AND CP.SectionID NOT IN (92,227)          
     AND NW.SectionID = 95  
 ORDER BY MM.Newslettersortorder 

如果您只是想要一个像以前一样的唯一列表，请执行此操作；

 SELECT DISTINCT
     CP.PostID
     ,CP.SectionID 
 FROM NewsLetter NW    
 INNER JOIN MapNewsletterPosts as MM 
     ON NW.ID = MM.ID          
 INNER JOIN CSPosts as CP with (nolock) 
     ON MM.PostID = CP.PostID         
 INNER JOIN PostStatus PS 
     ON PS.Postid=CP.PostId      
 INNER JOIN NewsletterDetails ND 
     ON ND.NewsletterDate = NW.NewsletterDate 
     AND ND.IncludeInArticles=1    
 WHERE NW.NewsletterDate = '2015-07-06'   
     AND CP.IsApproved =1                                             
     AND PS.StatusId =7        
     AND CP.SectionID NOT IN (92,227)          
     AND NW.SectionID = 95  
 ORDER BY MM.Newslettersortorder