Basic syntax of the FOR XML clause

Artikkeli
03/03/2023

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

The FOR XML mode can be RAW, AUTO, EXPLICIT, or PATH. It determines the shape of the resulting XML.

Important

The XMLDATA directive to the FOR XML option is deprecated. Use XSD generation in the case of RAW and AUTO modes. There is no replacement for the XMLDATA directive in EXPLICT mode. This feature will be removed in a future version of SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.

Syntax

Following is the basic syntax that is described in FOR Clause (Transact-SQL).

[ FOR { BROWSE | <XML> } ]
<XML> ::=
XML
    {
      { RAW [ ('ElementName') ] | AUTO }
        [
           <CommonDirectives>
           [ , { XMLDATA | XMLSCHEMA [ ('TargetNameSpaceURI') ]} ]
           [ , ELEMENTS [ XSINIL | ABSENT ]
        ]
      | EXPLICIT
        [
           <CommonDirectives>
           [ , XMLDATA ]
        ]
      | PATH [ ('ElementName') ]
        [
           <CommonDirectives>
           [ , ELEMENTS [ XSINIL | ABSENT ] ]
        ]
     }

<CommonDirectives> ::=
   [ , BINARY BASE64 ]
   [ , TYPE ]
   [ , ROOT [ ('RootName') ] ]

Syntax for Azure SQL Database

For documentation of the SELECT...FOR XML clause that also applies to Azure SQL Database, see FOR XML (SQL Server).

Arguments

RAW [('ElementName')]

Takes the query result and transforms each row in the result set into an XML element that has a generic identifier, <row />, as the element tag. You can optionally specify a name for the row element when you use this directive. The resulting XML will use the specified ElementName as the row element generated for each row. For more information, see Use RAW Mode with FOR XML.

AUTO

Returns query results in a simple, nested XML tree. Each table in the FROM clause for which at least one column is listed in the SELECT clause is represented as an XML element. The columns listed in the SELECT clause are mapped to the appropriate element attributes. For more information, see Use AUTO Mode with FOR XML.

EXPLICIT

Specifies that the shape of the resulting XML tree is defined explicitly. By using this mode, queries must be written in a particular way so additional information about the nesting you want is specified explicitly. For more information, see Use EXPLICIT Mode with FOR XML.

PATH

Provides a simpler way to mix elements and attributes, and to introduce additional nesting for representing complex properties. You can use FOR XML EXPLICIT mode queries to construct this kind of XML from a rowset, but the PATH mode provides a simpler alternative to the possibly cumbersome EXPLICIT mode queries. PATH mode, together with the ability to write nested FOR XML queries and the TYPE directive to return xml type instances, allows you to write queries with less complexity. It provides an alternative to writing most EXPLICIT mode queries. By default, PATH mode generates a <row> element wrapper for each row in the result set. You can optionally specify an element name. If you do, the specified name is used as the wrapper element name. If you provide an empty string (FOR XML PATH ('')), no wrapper element is generated. For more information, see Use PATH Mode with FOR XML.

MLDATA

Specifies that an inline XML-Data Reduced (XDR) schema should be returned. The schema is prepended to the document as an inline schema. For a working sample, see Use RAW Mode with FOR XML.

XMLSCHEMA

Returns an inline W3C XML Schema (XSD). You can optionally specify a target namespace URI when specifying this directive. This returns the specified namespace in the schema. For more information, see Generate an Inline XSD Schema. For a working sample, see Use RAW Mode with FOR XML.

ELEMENTS

If the ELEMENTS option is specified, the columns are returned as subelements. Otherwise, they're mapped to XML attributes. This option is supported in RAW, AUTO, and PATH modes only. You can optionally specify XSINIL or ABSENT when you use this directive. XSINIL specifies that an element that has an xsi:nil attribute set to True be created for NULL column values. By default or when ABSENT is specified together with ELEMENTS, no elements are created for NULL values. For a working sample, see Use RAW Mode with FOR XML and Use AUTO Mode with FOR XML.

BINARY BASE64

If the BINARY Base64 option is specified, any binary data returned by the query is represented in base64-encoded format. To retrieve binary data by using RAW and EXPLICIT mode, this option must be specified. In AUTO mode, binary data is returned as a reference by default. For a working sample, see Use RAW Mode with FOR XML.

TYPE

Specifies that the query returns the results as the xml type. For more information, see TYPE Directive in FOR XML Queries.

ROOT [('RootName')]

Specifies that a single, top-level element is added to the resulting XML. You can optionally specify the root element name to generate. The default value is <root>.

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