如何将CTE与for XML子句组合？

Question

我正在尝试生成一些具有各种嵌套级别的XML，并且冒着过度简化的危险，输出XML将宽松地与格式：

<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存储在不同表中的费用，这意味着附加费的存储方式不同，基于表格的表格。

鉴于你 不能用 UNION与 FOR XML, ，我做了一些 UNION在CTE中，因此沿着：

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，那是 令人难以置信的 关闭，给予（注意嵌套 <surcharge>):

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

但是，我需要找到一种获取最终查询的方法，以包括要将XML列的值视为元素的内容，而不是将其视为新元素。这是可能的，还是我需要采取新方法？

Answer 1

看来将（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，使其正常工作：

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 2

您有一个列查询，该查询返回mulitple行（@Charge，@rate和XML类型。）我希望您发布的查询会出现错误：

当不存在子查询时，在选择列表中只能指定一个表达式。

但是，通过将查询移至 outer apply. 。去除双人 surcharge 元素，您可以将XML列名称移至底部，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

例如，这将打印：

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

第一个元素来自联盟的顶部， surcharge = null.

Answer 3

我认为您可以通过省略“ for xml路径（'附加费'）”语句中的根节点类型来做到这一点。也就是说，使用“用于XML路径（''）”。