SQL Server 左连接没有给出正确的结果

Question

美好的一天，

我已经阅读了人们在使用左连接时面临的其他一些问题，没有给出正确的结果，也许我没有很好地理解所有的答案。

这是我在查询中遇到的问题

    SELECT 
       TA.column1
      ,D.column2
      ,D.column3
      ,TA.column4
      ,MI.[column5]
      ,MI.[column6]
      ,D.[column7]
      ,D.[column8]
      ,TA.[column9]
      ,TA.[column10]
      ,UC.[column11]
      ,UC.[column12]
      ,TA.[column13]
      ,TA.[column14]
      ,TA.[column15]
      ,TA.[column16]
      ,TA.[column17]
      ,'0' AS column18
      ,TA.[column19]
      ,'12.2' AS column20
      ,'None' AS column21
      ,'0' AS column22
      ,'1' AS column23
      ,TA.[column24]
      ,'0' AS column25
      ,'0' AS column26
      ,LD.column27
  FROM [DB].[dbo].[Table1] AS TA WITH (NOLOCK)
  FULL OUTER JOIN 
  [DB].[dbo].[Table2] AS LD WITH (NOLOCK)
  ON
  TA.[coulmn1]=LD.[coulmn5]
  INNER JOIN
  [DB].[dbo].[Table3] AS MI WITH (NOLOCK)
  ON
  TA.coulmn10 = MI.[coulmn3]
  LEFT JOIN
  [DB].[dbo].[Table4] AS D WITH (NOLOCK)
  ON
  TA.coulmn25 = D.coulmn1
  INNER JOIN
  [DB1].[dbo].[Table5] AS UC WITH (NOLOCK)
  ON
  TA.coulmn12 = UC.coulmn3

  WHERE  
  (LD.coulmn5 != TA.[coulmn1])
  AND
  (TA.[coulmn23]= '0')

问题是当我更新查询并删除时

FULL OUTER JOIN 
  [DB].[dbo].[Table2] AS LD WITH (NOLOCK)
  ON
  TA.[coulmn1]=LD.[coulmn5]

以及删除以下 where 子句：

  WHERE  
  (LD.coulmn5 != TA.[coulmn1])
  AND

我在右表的视图中有 3 个结果。这是正确的，因为一个结果尚未写入左表

当我放回左外连接和 where 子句时，我只能再次看到 2 个结果，如果最后一列 ,LD.column27 显示为 NULL 不会出现三个结果。 本专栏接受NOT NULL 这可能是我没有得到首选结果的原因吗？

Answer 1

使用 LEFT OUTER JOIN 代替 FULL OUTER JOIN 并删除 `WHERE (LD.coulmn5 != TA.coulmn1]) AND' 部分

试试这个：

SELECT 
       TA.column1
      ,D.column2
      ,D.column3
      ,TA.column4
      ,MI.[column5]
      ,MI.[column6]
      ,D.[column7]
      ,D.[column8]
      ,TA.[column9]
      ,TA.[column10]
      ,UC.[column11]
      ,UC.[column12]
      ,TA.[column13]
      ,TA.[column14]
      ,TA.[column15]
      ,TA.[column16]
      ,TA.[column17]
      ,'0' AS column18
      ,TA.[column19]
      ,'12.2' AS column20
      ,'None' AS column21
      ,'0' AS column22
      ,'1' AS column23
      ,TA.[column24]
      ,'0' AS column25
      ,'0' AS column26
      ,LD.column27
  FROM [DB].[dbo].[Table1] AS TA WITH (NOLOCK)
  LEFT OUTER JOIN [DB].[dbo].[Table2] AS LD WITH (NOLOCK) ON  TA.[coulmn1]=LD.[coulmn5]
  INNER JOIN  [DB].[dbo].[Table3] AS MI WITH (NOLOCK)  ON  TA.coulmn10 = MI.[coulmn3]
  LEFT JOIN  [DB].[dbo].[Table4] AS D WITH (NOLOCK)  ON  TA.coulmn25 = D.coulmn1
  INNER JOIN  [DB1].[dbo].[Table5] AS UC WITH (NOLOCK)  ON  TA.coulmn12 = UC.coulmn3
  WHERE   (TA.[coulmn23]= '0')

Answer 2

应该工作：

SELECT 
   TA.column1
  ,D.column2
  ,D.column3
  ,TA.column4
  ,MI.[column5]
  ,MI.[column6]
  ,D.[column7]
  ,D.[column8]
  ,TA.[column9]
  ,TA.[column10]
  ,UC.[column11]
  ,UC.[column12]
  ,TA.[column13]
  ,TA.[column14]
  ,TA.[column15]
  ,TA.[column16]
  ,TA.[column17]
  ,'0' AS column18
  ,TA.[column19]
  ,'12.2' AS column20
  ,'None' AS column21
  ,'0' AS column22
  ,'1' AS column23
  ,TA.[column24]
  ,'0' AS column25
  ,'0' AS column26
  ,LD.column27
 FROM [DB].[dbo].[Table1] AS TA WITH (NOLOCK)
 FULL OUTER JOIN 
  [DB].[dbo].[Table2] AS LD WITH (NOLOCK)
  ON
 TA.[coulmn1]=LD.[coulmn5]
 INNER JOIN
 [DB].[dbo].[Table3] AS MI WITH (NOLOCK)
ON
TA.coulmn10 = MI.[coulmn3]
LEFT JOIN
[DB].[dbo].[Table4] AS D WITH (NOLOCK)
ON
TA.coulmn25 = D.coulmn1
INNER JOIN
[DB1].[dbo].[Table5] AS UC WITH (NOLOCK)
ON
TA.coulmn12 = UC.coulmn3

WHERE  
(LD.coulmn5 is null)
AND
(TA.[coulmn23]= '0')