Question

我正在尝试使用T-Sql中的Merge语句构建优化的Slowly Changing Dimension。我编写了以下代码来处理SCD1和SCD2的更改，以及数据表中的正常插入，数据来自源表，Name和Age是SCD1列，Animal和Blood是SCD2列：

DECLARE @LoadingDate DATETIME
SET @LoadingDate = '2012-08-20 14:23:29.827'

--Handle SCD1 Changes
MERGE INTO Table_2 AS DIM
 USING SourceTable AS SRC
 ON (DIM.ID1 = SRC.ID1
    AND DIM.ID2 = SRC.ID2)
 WHEN MATCHED
    AND (DIM.Name <> SRC.Name 
      OR DIM.AGE <> SRC.AGE)
    THEN 
    UPDATE 
    SET DIM.Name = SRC.Name,
    DIM.Age = SRC.Age;

--Handle SCD2 Changes
INSERT INTO Table_2
    (ID1, ID2, --Business Key
     Name, Age, --SCD1 Columns
     Animal, Blood, --SCD2 Columns
     DateEffective, DateExpires)
 SELECT
    ID1, ID2, --Business Key
     Name, Age, --SCD1 Columns
     Animal, Blood, --SCD2 Columns
     DateEffective, DateExpires
FROM (
MERGE Table_2 AS DIM
 USING SourceTable AS SRC
 ON (DIM.ID1 = SRC.ID1
    AND DIM.ID2 = SRC.ID2)
 WHEN NOT MATCHED
  THEN INSERT VALUES 
  (SRC.ID1, SRC.ID2,
   SRC.Name, SRC.Age,
   SRC.Animal, SRC.Blood,
   @LoadingDate, NULL)
 WHEN MATCHED 
   AND DIM.DateExpires IS NULL
   AND (DIM.Animal != SRC.Animal
    OR DIM.Blood != SRC.Blood)
   THEN UPDATE SET DIM.DateExpires = @LoadingDate
 OUTPUT $action Action_Out,
   SRC.ID1, SRC.ID2,
   SRC.Name, SRC.Age,
   SRC.Animal, SRC.Blood,
   @LoadingDate AS DateEffective,
   NULL AS DateExpires) AS MERGE_OUT
 WHERE MERGE_OUT.Action_Out = 'UPDATE';

代码可以正常使用SCD1更改（代码的第一部分），但它给了我错误： enter image description here 尝试插入新行时出现错误，业务键ID1和ID2与数据表中的任何其他行不匹配，“Labus”是名称字段中的值。

两个表的设计如下图所示，但SourceTable没有管家列： enter image description here

我真的会提供一些帮助。谢谢！

Answer 1

由于错误表明隐式nvarchar到int转换出错，解决此问题的初始步骤是显式地转换所有nvarchar和int值（如下所示），然后检查是否仍然出现错误。

如果没有出现错误，则可以开始删除强制转换并将其归零到特定的int或nvarchar字段。

如果您收到错误，这可能是一个更具体的错误，可帮助您找出正在发生的代码部分。

DECLARE @LoadingDate DATETIME
SET @LoadingDate = '2012-08-20 14:23:29.827'

--Handle SCD1 Changes
MERGE INTO Table_2 AS DIM
    USING SourceTable AS SRC
    ON ( CAST(DIM.ID1 AS INT) = CAST(SRC.ID1 AS INT)
         AND CAST(DIM.ID2 AS INT) = CAST(caSSRC.ID2 AS INT)
       )
    WHEN MATCHED AND ( CAST(DIM.Name AS nvarchar(255)) <> CAST(SRC.Name AS nvarchar(255))
                       OR CAST(DIM.AGE AS nvarchar(255)) <> CAST(SRC.AGE AS nvarchar(255))
                     )
        THEN 
    UPDATE
          SET
            DIM.Name = CAST(SRC.Name AS nvarchar(255)) ,
            DIM.Age = CAST(SRC.Age AS nvarchar(255)) ;

--Handle SCD2 Changes
INSERT  INTO Table_2
        ( ID1 ,
          ID2 , --Business Key
          Name ,
          Age , --SCD1 Columns
          Animal ,
          Blood , --SCD2 Columns
          DateEffective ,
          DateExpires
        )
        SELECT  CAST(ID1 AS INT),
                CAST(ID2 AS INT) , --Business Key
                CAST(Name AS nvarchar(255)) ,
                CAST(Age AS nvarchar(255)) , --SCD1 Columns
                CAST(Animal AS nvarchar(255)) ,
                CAST(Blood AS nvarchar(255)) , --SCD2 Columns
                DateEffective ,
                DateExpires
        FROM    (
MERGE Table_2 AS DIM
    USING SourceTable AS SRC
    ON ( CAST(DIM.ID1 AS INT) = CAST(SRC.ID1 AS INT)
         AND CAST(DIM.ID2 AS INT) =  CAST(SRC.ID2 AS INT)
       )
    WHEN NOT MATCHED 
        THEN INSERT
          VALUES    ( CAST(SRC.ID1 AS INT) ,
                      CAST(SRC.ID2 AS INT) ,
                  CAST(SRC.Name AS NVARCHAR(255)),
                  CAST(SRC.Age AS NVARCHAR(255)),
                  CAST(SRC.Animal AS NVARCHAR(255)),
                  CAST(SRC.Blood  AS NVARCHAR(255)),
                      @LoadingDate ,
                      NULL
                    )
    WHEN MATCHED AND DIM.DateExpires IS NULL
        AND ( CAST(DIM.Animal AS NVARCHAR(255)) != CAST(SRC.Animal AS NVARCHAR(255))
              OR CAST(DIM.Blood AS NVARCHAR(255)) != CAST(SRC.Blood AS NVARCHAR(255))
            )
        THEN UPDATE
          SET       DIM.DateExpires = @LoadingDate
    OUTPUT
        $action Action_Out ,
        SRC.ID1 ,
        SRC.ID2 ,
        SRC.Name ,
        SRC.Age ,
        SRC.Animal ,
        SRC.Blood ,
        @LoadingDate AS DateEffective ,
        NULL AS DateExpires) AS MERGE_OUT
        WHERE   MERGE_OUT.Action_Out = 'UPDATE' ;
    --...
    --...
    --...

Answer 2

等等哦！最后一次合并的OUTPUT可能与Select子句不匹配。因此，Action_Out可能被映射到ID1，因此隐式转换尝试。

尝试修改OUTPUT子句，如下所示：

OUTPUT
    $action Action_Out ,
    SRC.ID1 AS ID1,
    SRC.ID2 AS ID2,
    SRC.Name AS Name,
    SRC.Age AS Age,
    SRC.Animal AS Animal,
    SRC.Blood AS Blood,
    @LoadingDate AS DateEffective ,
    NULL AS DateExpires) AS MERGE_OUT
    WHERE   MERGE_OUT.Action_Out = 'UPDATE' ;

Answer 3

试试这个：基本上，我在SELECT列中使用了别名（可组合DML仍有改进的余地。）

另外，当您在子查询中合并到Table_2中时，是否有理由再次将其他记录（用于更新操作）插入Table_2？

DECLARE @LoadingDate DATETIME
SET @LoadingDate = '2012-08-20 14:23:29.827'

--Handle SCD1 Changes
MERGE INTO Table_2 AS DIM
    USING SourceTable AS SRC
    ON ( DIM.ID1 = SRC.ID1
         AND DIM.ID2 = SRC.ID2
       )
    WHEN MATCHED AND ( DIM.Name <> SRC.Name
                       OR DIM.AGE <> SRC.AGE
                     )
        THEN 
    UPDATE
          SET
            DIM.Name = SRC.Name ,
            DIM.Age = SRC.Age ;

--Handle SCD2 Changes
INSERT  INTO Table_2
        ( ID1 ,
          ID2 , --Business Key
          Name ,
          Age , --SCD1 Columns
          Animal ,
          Blood , --SCD2 Columns
          DateEffective ,
          DateExpires
        )
        SELECT  MERGE_OUT.ID1 ,
                MERGE_OUT.ID2 , --Business Key
                MERGE_OUT.Name ,
                MERGE_OUT.Age , --SCD1 Columns
                MERGE_OUT.Animal ,
                MERGE_OUT.Blood , --SCD2 Columns
                MERGE_OUT.DateEffective ,
                MERGE_OUT.DateExpires
        FROM    (
MERGE INTO Table_2 AS DIM
    USING SourceTable AS SRC
    ON ( DIM.ID1 = SRC.ID1
         AND DIM.ID2 = SRC.ID2
       )
    WHEN NOT MATCHED 
        THEN INSERT
          VALUES    ( SRC.ID1 ,
                      SRC.ID2 ,
                      SRC.Name ,
                      SRC.Age ,
                      SRC.Animal ,
                      SRC.Blood ,
                      @LoadingDate ,
                      NULL
                    )
    WHEN MATCHED AND DIM.DateExpires IS NULL
        AND ( DIM.Animal != SRC.Animal
              OR DIM.Blood != SRC.Blood
            )
        THEN UPDATE
          SET       DIM.DateExpires = @LoadingDate
    OUTPUT
        $action AS Action_Out ,
        SRC.ID1 AS ID1 ,
        SRC.ID2 AS ID2 ,
        SRC.NAME AS Name ,
        SRC.Age AS Age ,
        SRC.Animal AS Animal ,
        SRC.Blood AS Blood ,
        @LoadingDate AS DateEffective ,
    NULL AS DateExpires) AS MERGE_OUT ( ID1, ID2, Name, Age, Animal, Blood,
                                        DateEffective, DateExpires )
        WHERE   MERGE_OUT.Action_Out = 'UPDATE' ;

T-SQL Merge语句中的T-SQL转换错误

3 个答案: