Question

我正在尝试生成一些具有各种嵌套级别的XML，并且存在过度简化的风险，输出XML将大致采用以下格式：

<invoice number="1">
 <charge code="foo" rate="123.00">
  <surcharge amount="10%" />
 </charge>
 <charge code="bar" />
</invoice>

我为此继承的数据库模式恰好将费用存储在不同的表中，这意味着根据收费来自的表格，附加费的存储方式不同。

鉴于你cannot use UNIONs with FOR XML，我在CTE中做了一些UNION，所以有以下几点：

WITH Charges ( [@code], [@rate], surcharge, InvoiceId ) AS (
    SELECT code AS [@Code], amount AS [@rate], NULL as surcharge, InvoiceId
    FROM item.charges
UNION ALL
    SELECT 
        code AS [@Code], 
        amount AS [@rate],
        (
             SELECT amount AS [@amount]
             FROM order.surcharges os
             WHERE oc.ChargeId = os.ChargeId
             FOR XML PATH('surcharge'), TYPE
        ), 
        InvoiceId
    FROM order.charges oc
)
SELECT
    Number AS [@number],
    (
         SELECT
             [@code],
             [@rate],
             surcharge
         FROM Charges
         WHERE Charges.InvoiceId = i.InvoiceId
    )
FROM Invoices i
FOR XML PATH( 'invoice' ), TYPE

现在，令人难以置信地关闭，给出（注意嵌套的<surcharge>）：

<invoice number="1">
 <charge code="foo" rate="123.00">
  <surcharge>
   <surcharge amount="10%" />
  </surcharge>
 </charge>
 <charge code="bar" />
</invoice>

但我需要找到一种方法来获取结束查询，以包含要被视为元素内容的XML列的值，而不是作为新元素。这是可能的，还是我需要采取新的方法？

Answer 1

你有一个列查询，它返回多行（@ charge，@rate和XML类型。）我希望你发布的查询给出错误：

只能指定一个表达式在子查询中的选择列表中没有引入EXISTS。

但是，通过将查询移至outer apply可以轻松解决此问题。要删除双surcharge元素，您可以将XML列名称尽可能地移动到底部，例如：

;WITH Charges (code, rate, surcharge, InvoiceId) AS 
    (
    SELECT  code, amount, NULL, InvoiceId
    FROM    @charges
    UNION ALL
    SELECT  code
    ,       amount
    ,       (
            SELECT  amount AS [@amount]
            FROM    @surcharges os
            WHERE   oc.ChargeId = os.ChargeId
            FOR XML PATH('surcharge'), TYPE
            )
    ,       InvoiceId
    FROM    @charges oc
)
SELECT  Number AS [@number]
,       c.code as [charge/@code]
,       c.rate as [charge/@rate]
,       c.surcharge as [charge]
FROM    @Invoices i
outer apply
        (
        SELECT  code
        ,       rate
        ,       surcharge
        FROM    Charges
        WHERE   Charges.InvoiceId = i.InvoiceId
        ) c
WHERE   i.InvoiceID = 1
FOR XML PATH( 'invoice' ), TYPE

这将打印，例如：

<invoice number="1">
  <charge code="1" rate="1" />
</invoice>
<invoice number="1">
  <charge code="1" rate="1">
    <surcharge amount="1" />
  </charge>
</invoice>

第一个元素来自联合的顶部，surcharge = null。

Answer 2

似乎将（假）列命名为“*”将使用该列的内容作为元素的内容，因此更改SQL如下所示：

WITH Charges ( [@code], [@rate], surcharge, InvoiceId ) AS (
    SELECT code AS [@Code], amount AS [@rate], NULL as surcharge, InvoiceId
    FROM item.charges
UNION ALL
    SELECT 
        code AS [@Code], 
        amount AS [@rate],
        (
             SELECT amount AS [@amount]
             FROM order.surcharges os
             WHERE oc.ChargeId = os.ChargeId
             FOR XML PATH('surcharge'), TYPE
        ), 
        InvoiceId
    FROM order.charges oc
)
SELECT
    Number AS [@number],
    (
         SELECT
             [@code],
             [@rate],
             surcharge AS [*] -- Thsi will embed the contents of the previously generated XML in here.
         FROM Charges
         WHERE Charges.InvoiceId = i.InvoiceId
    )
FROM Invoices i
FOR XML PATH( 'invoice' ), TYPE

Answer 3

我认为您可以通过省略“for xml path（'surcharge'）”语句中的根节点类型来实现此目的。也就是说，改为使用“for xml path（''）”。

如何将CTE与FOR XML子句结合使用？

3 个答案: