MYSQL – 展平表查询

2023年4月9日 132次阅读

我对下面的查询有一些问题,我不确定如何修改它以给我所需的输出,详情如下：

SELECT listup.NodeNumber As Node, listup.Station As Extension,
       CASE WHEN VoiceServer = 1 THEN KeyDescription ELSE '' END AS 'Key1',
       CASE WHEN VoiceServer = 2 THEN KeyDescription ELSE '' END AS 'Key2',
       CASE WHEN VoiceServer = 3 THEN KeyDescription ELSE '' END AS 'Key3',
       CASE WHEN VoiceServer = 4 THEN KeyDescription ELSE '' END AS 'Key4',
       CASE WHEN VoiceServer = 5 THEN KeyDescription ELSE '' END AS 'Key5',
       CASE WHEN VoiceServer = 6 THEN KeyDescription ELSE '' END AS 'Key6',
       CASE WHEN VoiceServer = 7 THEN KeyDescription ELSE '' END AS 'Key7',
       CASE WHEN VoiceServer = 8 THEN KeyDescription ELSE '' END AS 'Key8',
       CASE WHEN VoiceServer = 9 THEN KeyDescription ELSE '' END AS 'Key9',
       CASE WHEN VoiceServer = 10 THEN KeyDescription ELSE '' END AS 'Key10'
  FROM listup
ORDER BY listup.NodeNumber, listup.Station;

输出如下：

Node    Extension  Key1   Key2   Key3  etc.
N100    14311   14311                                    
N100    14311       14308                                
N100    14311           14309                            
N100    14311               14314                        
N100    14311                   14412                    
N100    14311                       14535                
N100    14311                           14316            
N100    14311                               14456        
N100    14312   14312                                    
N100    14312       14442                                
N100    14312           14311                            
N100    14312               14314                        
N100    14312                   14456                    
N100    14312                       14309                
N100    14312                           14308

我想把它全部出现在一条线上,所以这样扁平化了……
例如.

N100    14311   14311   14308   14309   14314  14412  14535  14316   14456
N100    14312   14312   14442   14311   14314  14456  14309  14308

最佳答案 您需要定义GROUP BY子句,并使用MAX聚合来获取所需的输出：

  SELECT listup.NodeNumber As Node, listup.Station As Extension,
         MAX(CASE WHEN VoiceServer = 1 THEN KeyDescription ELSE NULL END) AS 'Key1',
         MAX(CASE WHEN VoiceServer = 2 THEN KeyDescription ELSE NULL END) AS 'Key2',
         MAX(CASE WHEN VoiceServer = 3 THEN KeyDescription ELSE NULL END) AS 'Key3',
         MAX(CASE WHEN VoiceServer = 4 THEN KeyDescription ELSE NULL END) AS 'Key4',
         MAX(CASE WHEN VoiceServer = 5 THEN KeyDescription ELSE NULL END) AS 'Key5',
         MAX(CASE WHEN VoiceServer = 6 THEN KeyDescription ELSE NULL END) AS 'Key6',
         MAX(CASE WHEN VoiceServer = 7 THEN KeyDescription ELSE NULL END) AS 'Key7',
         MAX(CASE WHEN VoiceServer = 8 THEN KeyDescription ELSE NULL END) AS 'Key8',
         MAX(CASE WHEN VoiceServer = 9 THEN KeyDescription ELSE NULL END) AS 'Key9',
         MAX(CASE WHEN VoiceServer = 10 THEN KeyDescription ELSE NULL END) AS 'Key10'
    FROM listup
GROUP BY listup.NodeNumber As Node, listup.Station As Extension
ORDER BY listup.NodeNumber, listup.Station

NULL优于零长度字符串.

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