Question

我有以下声明：

MERGE dbo.SystemCustomer As TARGET
USING (Select * 
       From dbo.vClients 
       Where ClientNumber Is Not Null) As SOURCE
    On TARGET.CustNumber = SOURCE.ClientNumber
WHEN MATCHED And (TARGET.DisplayCustNumber<>SOURCE.VisualID Or 
                  TARGET.CustName<>ISNULL(SOURCE.CustName,'') 
             And IsNull(SOURCE.VisualID,'') <> '' And IsNull(TARGET.DisplayCustNumber,'') <> ''
THEN Update Set TARGET.DisplayCustNumber = SOURCE.VisualID,
                TARGET.CustName = ISNULL(SOURCE.CustName,'')    
WHEN NOT MATCHED BY TARGET
THEN Insert (CustNumber, DisplayCustNumber, CustName)
     Values (SOURCE.ClientNumber, SOURCE.VisualID, ISNULL(SOURCE.CustName,''))  
WHEN NOT MATCHED BY Source --or IsNull(TARGET.DisplayCustNumber,'') = ''
THEN Delete;

我想删除未与来源匹配的记录以及Target.DisplayCustNumber为空或null时的记录（在"WHEN NOT MATCHED BY Source"声明后的评论中说明） - 但显然不是可能的语法明智。我该如何绕过这个？提前谢谢！

Answer 1

如果没有您的表格定义，我无法真正测试，但您可以保留WHEN NOT MATCHED BY SOURCE THEN DELETE并添加另一个WHEN MATCHED AND <condition> THEN DELETE。

MERGE dbo.SystemCustomer As TARGET
USING (Select * 
       From dbo.vClients 
       Where ClientNumber Is Not Null) As SOURCE
    On TARGET.CustNumber = SOURCE.ClientNumber
WHEN MATCHED And (TARGET.DisplayCustNumber<>SOURCE.VisualID Or 
                  TARGET.CustName<>ISNULL(SOURCE.CustName,'') 
             And IsNull(SOURCE.VisualID,'') <> '' And IsNull(TARGET.DisplayCustNumber,'') <> ''
THEN Update Set TARGET.DisplayCustNumber = SOURCE.VisualID,
                TARGET.CustName = ISNULL(SOURCE.CustName,'')   

WHEN MATCHED AND IsNull(TARGET.DisplayCustNumber,'') = '' THEN DELETE -- Add this line

WHEN NOT MATCHED BY TARGET
THEN Insert (CustNumber, DisplayCustNumber, CustName)
     Values (SOURCE.ClientNumber, SOURCE.VisualID, ISNULL(SOURCE.CustName,''))  
WHEN NOT MATCHED BY Source --or IsNull(TARGET.DisplayCustNumber,'') = ''
THEN Delete;

多个MATCHED语句有一些限制，但它们适用于您的情况（如果您进一步编辑，请留意）：

MERGE语句最多可以有两个WHEN MATCHED子句。如果两个条款是指定的，那么第一个条款必须附有一个 AND条款。对于任何给定的行，仅第二个WHEN MATCHED子句如果第一个不是，则应用。如果有两个WHEN MATCHED条款，然后必须指定UPDATE操作，并且必须指定DELETE 行动。如果在子句中指定了UPDATE，则多行匹配target_table中的一行，SQL Server返回错误。 MERGE语句不能多次更新同一行，或更新并删除同一行。

如何在合并条件中使用“或”“何时不与源匹配”

1 个答案: