SQL Server : Merge across multiple tables with foreign key - sql

Question

Here's what I am trying to do: basically send XML to SQL Server to update/insert (Merge) my data as a "save" function in my code.
I have managed to successfully do this if I send one "item" in the XML using the following XML:
<root>
<Formula1>
<M_iFormula1Id>0</M_iFormula1Id>
<M_bDataInUse>0</M_bDataInUse>
<M_bActive>1</M_bActive>
<M_lstItem>
<M_iItemId>0</M_iItemId>
<M_iItemTypeId>1</M_iItemTypeId>
<M_sItemValue>German</M_sItemValue>
<M_iRaceId>1</M_iRaceId>
<M_iDriverId>50</M_iDriverId>
</M_lstItem>
</Formula1>
</root>
in this stored procedure:
ALTER PROCEDURE [dbo].[spFormula1_Save]
#Formula1Xml xml--Formula1 as xml
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;
IF DATALENGTH(#Formula1Xml) = 0
RETURN 0
BEGIN TRANSACTION
BEGIN TRY
DECLARE #hDoc INT
EXEC sp_xml_preparedocument #hDoc OUTPUT, #Formula1Xml
-------------------
--Formula1 Table
-------------------
DECLARE #Formula1Id bigint = 0;
MERGE INTO Formula1 AS tab
USING
OPENXML (#hDoc, '/root/Formula1', 2)
WITH (
M_iFormula1Id bigint,
M_bDataInUse bit,
M_bActive bit
) AS [xml]
ON (tab.Formula1Id = [xml].[M_iFormula1Id])
WHEN MATCHED THEN UPDATE SET tab.DataInUse = [xml].M_bDataInUse,
tab.Active = [xml].M_bActive,
#Formula1Id = [xml].M_iFormula1Id
WHEN NOT MATCHED THEN INSERT (DataInUse,
Active)
VALUES([xml].M_bDataInUse,
[xml].M_bActive
);
IF(#Formula1Id = 0)--then we haven''t updated so get inserted rowid
BEGIN
SET #Formula1Id = SCOPE_IDENTITY();--get the inserted identity
END
-------------------
--Formula1Item Table
-------------------
MERGE INTO Formula1Item AS tab
USING
OPENXML (#hDoc, '/root/Formula1/M_lstItem', 2)
WITH (
M_iItemId bigint,
M_iItemTypeId bit,
M_sItemValue varchar(1000),
M_iRaceId int,
M_iDriverId int
) AS [xml]
ON (tab.ItemId = [xml].M_iItemId)
WHEN MATCHED THEN UPDATE SET tab.ItemTypeId = [xml].M_iItemTypeId,
tab.ItemValue = [xml].M_sItemValue,
tab.RaceId = [xml].M_iRaceId,
tab.DriverId = [xml].M_iDriverId
WHEN NOT MATCHED THEN INSERT (Formula1Id,
ItemTypeId,
ItemValue,
RaceId,
DriverId)
VALUES(#Formula1Id,
[xml].M_iItemTypeId,
[xml].M_sItemValue,
[xml].M_iRaceId,
[xml].M_iDriverId
);
COMMIT TRANSACTION;
END TRY
BEGIN CATCH
ROLLBACK TRANSACTION;
END CATCH;
END
When I have multiple records in the XML the #Formula1Id gets set to the last one inserted in the first merge statement so all the Child data in the XML gets merged using this id, meaning all child data belongs to one parent!
<root>
<Formula1>
<M_iFormula1Id>0</M_iFormula1Id>
<M_bDataInUse>0</M_bDataInUse>
<M_bActive>1</M_bActive>
<M_lstItem>
<M_iItemId>0</M_iItemId>
<M_iItemTypeId>1</M_iItemTypeId>
<M_sItemValue>German</M_sItemValue>
<M_iRaceId>1</M_iRaceId>
<M_iDriverId>50</M_iDriverId>
</M_lstItem>
</Formula1>
<Formula1>
<M_iFormula1Id>0</M_iFormula1Id>
<M_bDataInUse>0</M_bDataInUse>
<M_bActive>1</M_bActive>
<M_lstItem>
<M_iItemId>0</M_iItemId>
<M_iItemTypeId>1</M_iItemTypeId>
<M_sItemValue>French</M_sItemValue>
<M_iRaceId>2</M_iRaceId>
<M_iDriverId>50</M_iDriverId>
</M_lstItem>
</Formula1>
</root>
Is there any way to perform this keeping the foreign key relationship correct.
Perhaps the Merge statement is the wrong way to go but it seems like the best way to handle a lot of inserts/updates at once.
Maybe you could suggest an alternative method - the main criteria is performance as there could be thousands of items to "save" - I have tried to look at SqlBulkCopy but this doesn't seem to handle foreign key relationships very well either... I know I could save to one table at a time but then I lose the ROLLBACK functionality should one part of the "save" go wrong!
Any help/suggestions are greatly appreciated. Thanks in advance.

Answer 1

Try using following solution (it's not tested; I assumed that you can have many "Formula1" elements; you should carefully read my notes):
ALTER PROCEDURE [dbo].[spFormula1_Save]
#Formula1Xml xml--Formula1 as xml
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT, XACT_ABORT ON;
IF DATALENGTH(#Formula1Xml) = 0
RETURN 0
------------------------
--Xml shredding
------------------------
-- I prefer using the new XML methods (nodes, value, exist) instead of sp_xml_preparedocument + OPENXML
-- because you may get memory leaks if we don't use sp_xml_removedocument
DECLARE #Formula1_Table TABLE
(
M_iFormula1Id bigint,
Rnk bigint primary key, -- It's used to unique identify the old and the new rows
M_bDataInUse bit,
M_bActive bit
);
INSERT #Formula1_Table (M_iFormula1Id, Rnk, M_bDataInUse, M_bActive)
SELECT x.XmlCol.value('(M_iFormula1Id)[1]', 'BIGINT') AS M_iFormula1Id,
ROW_NUMBER() OVER(ORDER BY x.XmlCol) AS Rnk, -- It's used to unique identify the old and the new rows
x.XmlCol.value('(M_bDataInUse)[1]', 'BIT') AS M_bDataInUse,
x.XmlCol.value('(M_bActive)[1]', 'BIT') AS M_bActive
FROM #Formula1Xml.nodes('/root/Formula1') x(XmlCol);
DECLARE #Formula1_M_lstItem_Table TABLE
(
M_iFormula1Id bigint,
Rnk bigint, -- It's used to unique identify new "Formula1" rows (those rows having M_iFormula1Id=0)
M_iItemId bigint,
M_iItemTypeId bit,
M_sItemValue varchar(1000),
M_iRaceId int,
M_iDriverId int
);
INSERT #Formula1_M_lstItem_Table
(
M_iFormula1Id,
Rnk,
M_iItemId,
M_iItemTypeId,
M_sItemValue,
M_iRaceId,
M_iDriverId
)
SELECT /*x.XmlCol.value('(M_iFormula1Id)[1]', 'BIGINT')*/
-- At this moment we insert only nulls
NULL AS M_iFormula1Id,
DENSE_RANK() OVER(ORDER BY x.XmlCol) AS Rnk, -- It's used to unique identify new and old "Formula1" rows
y.XmlCol.value('(M_iItemId)[1]', 'BIGINT') AS M_iItemId,
y.XmlCol.value('(M_iItemTypeId)[1]', 'BIT') AS M_iItemTypeId,
y.XmlCol.value('(M_sItemValue)[1]', 'VARCHAR(1000)') AS M_sItemValue,
y.XmlCol.value('(M_iRaceId)[1]', 'INT') AS M_iRaceId,
y.XmlCol.value('(M_iDriverId)[1]', 'INT') AS M_iDriverId
FROM #Formula1Xml.nodes('/root/Formula1') x(XmlCol)
CROSS APPLY x.XmlCol.nodes('M_lstItem') y(XmlCol);
------------------------
--End of Xml shredding
------------------------
BEGIN TRANSACTION
BEGIN TRY
-------------------
--Formula1 Table
-------------------
DECLARE #Merged_Rows TABLE
(
Merge_Action nvarchar(10) not null,
Rnk bigint not null,
M_iFormula1Id bigint -- The old id's and the new inserted id's.
);
DECLARE #Formula1Id bigint = 0;
MERGE INTO Formula1 WITH(HOLDLOCK) AS tab -- To prevent race condition. http://weblogs.sqlteam.com/dang/archive/2009/01/31/UPSERT-Race-Condition-With-MERGE.aspx
USING #Formula1_Table AS [xml]
ON (tab.Formula1Id = [xml].[M_iFormula1Id])
WHEN MATCHED THEN UPDATE SET tab.DataInUse = [xml].M_bDataInUse,
tab.Active = [xml].M_bActive
-- We no more need this line because of OUTPUT clause
-- #Formula1Id = [xml].M_iFormula1Id
WHEN NOT MATCHED THEN INSERT (DataInUse,
Active)
VALUES([xml].M_bDataInUse,
[xml].M_bActive
)
-- This OUTPUT clause will insert into #Merged_Rows the Rnk and the new M_iFormula1Id for every /root/Formula1 element
-- http://msdn.microsoft.com/en-us/library/ms177564.aspx
OUTPUT $action, [xml].Rnk, inserted.M_iFormula1Id INTO #Merged_Rows (Merge_Action, Rnk, M_iFormula1Id);
-- This is replaced by previous OUTPUT clause
/*
IF(#Formula1Id = 0)--then we haven''t updated so get inserted rowid
BEGIN
SET #Formula1Id = SCOPE_IDENTITY();--get the inserted identity
END
*/
-- At this moment we replace all previously inserted NULLs with the real (old and new) id's
UPDATE x
SET M_iFormula1Id = y.M_iFormula1Id
FROM #Formula1_M_lstItem_Table x
JOIN #Merged_Rows y ON x.Rnk = y.Rnk;
-------------------
--Formula1Item Table
-------------------
MERGE INTO Formula1Item AS tab
USING #Formula1_M_lstItem_Table AS [xml]
ON (tab.ItemId = [xml].M_iItemId)
-- Maybe you should need also this join predicate (tab.M_iFormula1Id = [xml].M_iFormula1Id)
WHEN MATCHED THEN UPDATE SET tab.ItemTypeId = [xml].M_iItemTypeId,
tab.ItemValue = [xml].M_sItemValue,
tab.RaceId = [xml].M_iRaceId,
tab.DriverId = [xml].M_iDriverId
WHEN NOT MATCHED THEN INSERT (Formula1Id,
ItemTypeId,
ItemValue,
RaceId,
DriverId)
VALUES([xml].M_iFormula1Id,
[xml].M_iItemTypeId,
[xml].M_sItemValue,
[xml].M_iRaceId,
[xml].M_iDriverId
);
COMMIT TRANSACTION;
END TRY
BEGIN CATCH
ROLLBACK TRANSACTION;
-- The caller should be informed when an error / exception is catched
-- THROW
END CATCH;
END