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Example: Specify the ELEMENT directive and entity encoding

  • Artikkeli

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance

This example illustrates the difference between the ELEMENT and XML directives. The ELEMENT directive entitizes the data, but the XML directive doesn't. The <Summary> element is assigned XML, <Summary>This is summary description</Summary>, in the query.

Consider this query:

USE AdventureWorks2022;
GO
SELECT  1 as Tag,
        0 as Parent,
        ProductModelID  as [ProductModel!1!ProdModelID],
        Name            as [ProductModel!1!Name],
        NULL            as [Summary!2!SummaryDescription!ELEMENT]
FROM    Production.ProductModel
WHERE   ProductModelID=19
UNION ALL
SELECT  2 as Tag,
        1 as Parent,
        ProductModelID,
        NULL,
       '<Summary>This is summary description</Summary>'
FROM   Production.ProductModel
WHERE  ProductModelID = 19
FOR XML EXPLICIT;

This is the result. The summary description is entitized in the result.

<ProductModel ProdModelID="19" Name="Mountain-100">
  <Summary>
    <SummaryDescription><Summary>This is summary description</Summary></SummaryDescription>
  </Summary>
</ProductModel>

Now, if you specify the XML directive in the column name, Summary!2!SummaryDescription!XML, instead of the ELEMENT directive, you'll receive the summary description without entitization.

<ProductModel ProdModelID="19" Name="Mountain-100">
  <Summary>
    <SummaryDescription>
      <Summary>This is summary description</Summary>
    </SummaryDescription>
  </Summary>
</ProductModel>

Instead of assigning a static XML value, the following query uses the query() method of the xml type to retrieve the product model summary description from the CatalogDescription column of xml type. Because the result is known to be of xml type, no entitization is applied.

SELECT  1 as Tag,
        0 as Parent,
        ProductModelID  as [ProductModel!1!ProdModelID],
        Name            as [ProductModel!1!Name],
        NULL            as [Summary!2!SummaryDescription]
FROM    Production.ProductModel
WHERE   CatalogDescription is not null
UNION ALL
SELECT  2 as Tag,
        1 as Parent,
        ProductModelID,
        Name,
       (SELECT CatalogDescription.query('
            declare namespace pd="http://schemas.microsoft.com/sqlserver/2004/07/adventure-works/ProductModelDescription";
			/pd:ProductDescription/pd:Summary'))
FROM     Production.ProductModel
WHERE    CatalogDescription is not null
ORDER BY [ProductModel!1!ProdModelID],Tag
FOR XML EXPLICIT;

See also