SCD2 + Merge Statement + SQL Server

Question

I am trying work out with MERGE statment to Insert / Update Dimension Table of Type SCD2

My source is a Table var to Merge with Dimension table.

My MERGE statement is throwing an error as:

The target table 'DM.DATA_ERROR.ERROR_DIMENSION' of the INSERT statement cannot be on either side of a (primary key, foreign key) relationship when the FROM clause contains a nested INSERT, UPDATE, DELETE, or MERGE statement. Found reference constraint 'FK_ERROR_DIMENSION_to_AUDIT_CreatedBy'.

My MERGE Statement:

DECLARE @DATAERROROBJECT AS [ERROR_DIMENSION]

INSERT INTO DM.DATA_ERROR.ERROR_DIMENSION
SELECT  ERROR_CODE,
    DATA_STREAM_ID,
    [ERROR_SEVERITY],
    DATA_QUALITY_RATING,
    ERROR_LONG_DESCRIPTION,
    ERROR_DESCRIPTION,
    VALIDATION_RULE,
    ERROR_TYPE,
    ERROR_CLASS,
    VALID_FROM,
    VALID_TO,
    CURR_FLAG,
    CREATED_BY_AUDIT_SK,
    UPDATED_BY_AUDIT_SK

FROM (MERGE DM.DATA_ERROR.ERROR_DIMENSION ED USING @DATAERROROBJECT OBJ
     ON(ED.ERROR_CODE = OBJ.ERROR_CODE AND ED.DATA_STREAM_ID = OBJ.DATA_STREAM_ID)     WHEN NOT MATCHED THEN    INSERT VALUES(
         OBJ.ERROR_CODE
        ,OBJ.DATA_STREAM_ID
        ,OBJ.[ERROR_SEVERITY]
        ,OBJ.DATA_QUALITY_RATING
        ,OBJ.ERROR_LONG_DESCRIPTION
        ,OBJ.ERROR_DESCRIPTION
        ,OBJ.VALIDATION_RULE
        ,OBJ.ERROR_TYPE
        ,OBJ.ERROR_CLASS
        ,GETDATE()
        ,'9999-12-13'
        ,'Y'
        ,1
        ,1
        ) WHEN MATCHED AND ED.CURR_FLAG = 'Y'
             AND (      ED.[ERROR_SEVERITY] <> OBJ.[ERROR_SEVERITY]
                   OR   ED.[DATA_QUALITY_RATING] <> OBJ.[DATA_QUALITY_RATING]
                   OR   ED.[ERROR_LONG_DESCRIPTION] <> OBJ.[ERROR_LONG_DESCRIPTION]
                   OR   ED.[ERROR_DESCRIPTION] <> OBJ.[ERROR_DESCRIPTION]
                   OR   ED.[VALIDATION_RULE] <> OBJ.[VALIDATION_RULE]
                   OR   ED.[ERROR_TYPE] <> OBJ.[ERROR_TYPE]
                   OR   ED.[ERROR_CLASS] <> OBJ.[ERROR_CLASS] ) THEN UPDATE SET ED.CURR_FLAG = 'N', ED.VALID_TO = GETDATE()
        OUTPUT $ACTION ACTION_OUT, 
                           OBJ.ERROR_CODE ERROR_CODE,
                           OBJ.DATA_STREAM_ID DATA_STREAM_ID,
                           OBJ.[ERROR_SEVERITY] [ERROR_SEVERITY],
                           OBJ.DATA_QUALITY_RATING DATA_QUALITY_RATING,
                           OBJ.ERROR_LONG_DESCRIPTION ERROR_LONG_DESCRIPTION,
                           OBJ.ERROR_DESCRIPTION ERROR_DESCRIPTION,
                           OBJ.VALIDATION_RULE VALIDATION_RULE,
                           OBJ.ERROR_TYPE ERROR_TYPE,
                           OBJ.ERROR_CLASS ERROR_CLASS,
                           GETDATE() VALID_FROM,
                           '9999-12-31' VALID_TO,
                           'Y' CURR_FLAG,
                           555 CREATED_BY_AUDIT_SK,
                           555 UPDATED_BY_AUDIT_SK
                           ) AS MERGE_OUT WHERE MERGE_OUT.ACTION_OUT = 'UPDATE';

What am I doing wrong ?

Answer 1

I think your fundamental error is the fact that you seem to expect that MERGE is returning a data set - like SELECT .... does - it does not.

I don't believe you can use

SELECT (list of fields)
FROM (MERGE DM.DATA_ERROR.ERROR_DIMENSION ED 
      USING @DATAERROROBJECT OBJ
      ON(ED.ERROR_CODE = OBJ.ERROR_CODE AND ED.DATA_STREAM_ID = OBJ.DATA_STREAM_ID)
   .......

What you need to do is:

• load your data to be merged into a separate staging table
• then issue a MERGE statement as a separate statement against the target table, using that staging table as your source

Check out these resources:

• Using SQL Server 2008 MERGE statement
• SQL Server 2008: Introduction to MERGE