SQL 合并父子数据列表

Question

我有一个数据列表，要作为 XML 传递给存储过程。数据是 Widget 的列表，小部件包含 WidgetItem 的列表（父子数据）。我想做一个 MERGE 基于 Widget 的一个子集基于 ParentID。 ParentID 的一些数据已更新，一些已被删除（因此从 xml 中丢失）并且一些数据是新的。

更新的数据永远不需要更新子数据，因为Widget记录只能调整，而不是其中的项目（子数据）。 Insert 总会有一个或多个子记录（WidgetItems）。

我似乎无法弄清楚如何在 MERGE 中执行此操作，因为与在数据层中处理合并相比，这似乎是最好的方法。

这是我目前所知道的...我在卡住的地方发表了评论：

CREATE PROCEDURE dbo.pWidgetsMerge
    @Widgets XML
AS

/*
Assumed XML input @Widgets xml:
<Widgets>
    <Widget>
        <WidgetID>
        <ParentID>
        <StartDate>
        <EndDate>
        <Details>
            <WidgetDetailItem>
                <WidgetDetailItemID>
                <WidgetID>
                <SomeID>                
                <SomeData>
*/

MERGE
    [dbo].[Widget] as w  
USING
    (
        SELECT
            'WidgetID' = P.value('WidgetID[1]', 'INT'),
            'ParentID' = P.value('ParentID[1]', 'INT'),
            'StartDate' = P.value('EffectiveStartDate[1]', 'DATETIME'),
            'EndDate' = P.value('EffectiveEndDate[1]', 'DATETIME')
        FROM
            @Widgets.nodes('/Widgets/Widget') PROPERTYFEED(P)
    ) 
    AS xmlIn
    (
        [WidgetID],
        [StartDate],
        [EndDate]
    )
    ON
        w.[WidgetID] = xmlIn.[WidgetID]
    WHEN
        NOT MATCHED
    THEN
        INSERT 
        (
            [ParentID],
            [StartDate],
            [EndDate]
        ) 
        VALUES
        (
            xmlIn.[ParentID],
            xmlIn.[StartDate],
            xmlIn.[EndDate]
        )


        /*STUCK HERE: After the insert, need to put in the child
            records into a new table [WidgetItems].  Maybe it's another
            operation outside of the merge?*/

    WHEN
        MATCHED AND (
            (w.[StartDate] <> xmlIn.[StartDate]) OR 
            (w.[EndDate] <> xmlIn.[EndDate]))
    THEN
        UPDATE SET
            w.[StartDate] = xmlIn.[StartDate],
            w.[EndDate] = xmlIn.[EndDate]
    WHEN
        NOT MATCHED BY SOURCE AND w.[ParentID] = xmlIn.[ParentID]
    THEN
        UPDATE SET
            w.[DeletedDate] = GETDATE()

此外，如果我处理这个错误，我们将不胜感激，或者我可能确实需要在数据层处理这个问题。

Answer 1

我已经将传入的 XML 反序列化为 table。这让我们有机会验证 XML 字符串中的数据。

项目 1：新的反序列化 table 将提供一种简单的方法来过滤哪些数据包含在 MERGE 中。

项目 2：将数据插入子项 table 必须单独调用。 MERGE 只能处理一个 table 上的 CRUD（创建更新删除）操作。

注意：MERGE 将使用 DESTINATION table 中的所有记录。因此，当您与 Source 不匹配时，这将对未包含在 table.

中的所有记录起作用

Answer 2

下面是更新后的代码，应该可以回答您的问题。我添加了评论来解释发生了什么。希望它有意义。

如您所述，ParentID 对于传入的所有 Widget 都是相同的，因此我将其视为参数而不是 XML

的元素

DECLARE @ParentID INT = 1

DECLARE @Widgets AS XML = 
N'<Widgets>
    <Widget>
        <WidgetID />
        <StartDate />
        <EndDate />
        <Details>
            <WidgetDetailItem>
                <WidgetDetailItemID></WidgetDetailItemID>
                <WidgetID/>
                <SomeID>4</SomeID>             
                <SomeData/>
            </WidgetDetailItem>
            <WidgetDetailItem>
                <WidgetDetailItemID></WidgetDetailItemID>
                <WidgetID/>
                <SomeID>323</SomeID>             
                <SomeData/>
            </WidgetDetailItem>
            <WidgetDetailItem>
                <WidgetDetailItemID></WidgetDetailItemID>
                <WidgetID/>
                <SomeID>1</SomeID>            
                <SomeData/>
            </WidgetDetailItem>
        </Details>
    </Widget>
    <Widget>
        <WidgetID>10</WidgetID>
        <StartDate>January 1, 2015</StartDate>
        <EndDate />
        <Details>
            <WidgetDetailItem>
                <WidgetDetailItemID></WidgetDetailItemID>
                <WidgetID/>
                <SomeID>4</SomeID>         
                <SomeData/>
            </WidgetDetailItem>
            <WidgetDetailItem>
                <WidgetDetailItemID></WidgetDetailItemID>
                <WidgetID/>
                <SomeID>99</SomeID>         
                <SomeData/>
            </WidgetDetailItem>
            <WidgetDetailItem>
                <WidgetDetailItemID></WidgetDetailItemID>
                <WidgetID/>
                <SomeID>6</SomeID>            
                <SomeData/>
            </WidgetDetailItem>
        </Details>
    </Widget>
</Widgets>';

--Used to hold the pseudoID -> WidgetID relationship for inserting the details
DECLARE @WidgetIds AS TABLE ([Action] varchar(10), PseudoID INT, WidgetID INT);

; 
--Use a CTE of the subset of data to be more performant. If we just went straight to the 
--merge we'd be operating on the entire table and that can have some major performance hits
WITH T AS (
              SELECT 
                     w.* 
              FROM
                     [dbo].[Widget] as w 
              WHERE
                     w.[ParentID] = @ParentID
)
MERGE INTO T 
USING (
        SELECT
            --Generate a pseudoid based on the order of the Widget elements so that we have some way of 
            --linking the detail records to the master
            row_number() OVER(ORDER BY PROPERTYFEED.P) PseudoID,
            'WidgetID' = P.value('WidgetID[1]', 'INT'),
            'ParentID' = @ParentID,
            'StartDate' = P.value('StartDate[1]', 'DATETIME'),
            'EndDate' = P.value('EndDate[1]', 'DATETIME')
        FROM
            @Widgets.nodes('/Widgets/Widget') PROPERTYFEED(P)
    ) 
    AS xmlIn
    (
           [PseudoID],
        [WidgetID],
        [ParentID],
        [StartDate],
        [EndDate]
    )
    ON
        T.[WidgetID] = xmlIn.[WidgetID]
    WHEN
        NOT MATCHED
    THEN
        INSERT 
        (
            [ParentID],
            [StartDate],
            [EndDate]
        ) 
        VALUES
        (
            xmlIn.[ParentID],
            xmlIn.[StartDate],
            xmlIn.[EndDate]
        )
    WHEN
        MATCHED AND (
            (T.[StartDate] <> xmlIn.[StartDate]) OR 
            (T.[EndDate] <> xmlIn.[EndDate]))
    THEN
        UPDATE SET
            T.[StartDate] = xmlIn.[StartDate],
            T.[EndDate] = xmlIn.[EndDate]
    WHEN
        NOT MATCHED BY SOURCE AND T.[DeletedDate] IS NULL 
    THEN
        UPDATE SET
            T.[DeletedDate] = GETDATE()         
OUTPUT  $action, xmlIn.PseudoID, INSERTED.WidgetID INTO @WidgetIds

;

--This is some magic to generate a temp table of numbers from 1 to COUNT(Widget)
--This is so we can reference the parent Widget row in the same order as the pseudoid generated above
--
;WITH Total(TotalWidgets) AS (SELECT COUNT(1) TotalWidgets FROM @Widgets.nodes('/Widgets/Widget') PROPERTYFEED(P))
       , Numbers(Num) as (
              SELECT 1 AS Num
              UNION ALL 
              SELECT Num+1 
              FROM Numbers
              JOIN Total t ON 1 = 1
              WHERE Num < t.TotalWidgets )
INSERT INTO WidgetDetailItem (WidgetID,SomeID,SomeData)
SELECT 
       w.WidgetID
       ,Details.SomeID
       ,Details.SomeData
FROM 
    (SELECT 
        P.value('WidgetDetailItemID[1]','int')  WidgetDetailItemID           
        , P.value('SomeID[1]','int') SomeID
        , P.value('SomeData[1]','varchar(5)') SomeData
        , n.Num AS PsuedoID
    FROM Numbers n
    --This is what gives us our pseudo ID to link to the row_number() function from the first merge statement
    CROSS APPLY @Widgets.nodes('/Widgets/Widget[sql:column("n.Num")]/Details/WidgetDetailItem') AS M(P)
    ) Details
JOIN @WidgetIds w on Details.PsuedoID = w.PseudoID
WHERE w.Action = 'INSERT' --We only want inserts by your spec

SELECT * FROM Widget;
SELECT * FROM WidgetDetailItem;

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