| title | description | author | ms.author | ms.date | ms.service | ms.subservice | ms.topic | helpviewer_keywords | dev_langs | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
expanded-QName (XQuery) |
Learn how to use the expanded-QName() function to return the namespace URI and local name part of a QName. |
rothja |
jroth |
03/14/2017 |
sql |
xml |
reference |
|
|
[!INCLUDE SQL Server Azure SQL Database]
Returns a value of the xs:QName type with the namespace URI specified in the $paramURI and the local name specified in the $paramLocal. If $paramURI is the empty string or the empty sequence, it represents no namespace.
fn:expanded-QName($paramURI as xs:string?, $paramLocal as xs:string?) as xs:QName?
$paramURI
Is the namespace URI for the QName.
$paramLocal
Is the local name part of the QName.
The following applies to the expanded-QName() function:
-
If the $paramLocal value specified is not in the correct lexical form for xs:NCName type, the empty sequence is returned and represents a dynamic error.
-
Conversion from xs:QName type to any other type is not supported in [!INCLUDEssNoVersion]. Because of this, the expanded-QName() function cannot be used in XML construction. For example, when you are constructing a node, such as
<e> expanded-QName(...) </e>, the value has to be untyped. This would require that you convert the xs:QName type value returned byexpanded-QName()to xdt:untypedAtomic. However, this is not supported. A solution is provided in an example later in this topic. -
You can modify or compare the existing QName type values. For example,
/root[1]/e[1] eq expanded-QName("http://nsURI" "myNS")compares the value of the element, <e>, with the QName returned by the expanded-QName() function.
This topic provides XQuery examples against XML instances that are stored in various xml type columns in the [!INCLUDEssSampleDBobject] database.
This example illustrates how you can modify the value of an element node of QName type. The example performs the following:
-
Creates an XML schema collection that defines an element of QName type.
-
Creates a table with an xml type column by using the XML schema collection.
-
Saves an XML instance in the table.
-
Uses the modify() method of the xml data type to modify the value of the QName type element in the instance. The expanded-QName() function is used to generate the new QName type value.
-- If XML schema collection (if exists)
-- drop xml schema collection SC
-- go
-- Create XML schema collection
CREATE XML SCHEMA COLLECTION SC AS N'
<schema xmlns="http://www.w3.org/2001/XMLSchema"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="QNameXSD"
xmlns:xqo="QNameXSD" elementFormDefault="qualified">
<element name="Root" type="xqo:rootType" />
<complexType name="rootType">
<sequence minOccurs="1" maxOccurs="1">
<element name="ElemQN" type="xs:QName" />
</sequence>
</complexType>
</schema>'
go
-- Create table.
CREATE TABLE T( XmlCol xml(SC) )
-- Insert sample XML instance
INSERT INTO T VALUES ('
<Root xmlns="QNameXSD" xmlns:ns="https://myURI">
<ElemQN>ns:someName</ElemQN>
</Root>')
go
-- Verify the insertion
SELECT * from T
go
-- Result
<Root xmlns="QNameXSD" xmlns:ns="https://myURI">
<ElemQN>ns:someName</ElemQN>
</Root>
In the following query, the <ElemQN> element value is replaced by using the modify() method of the xml data type and the replace value of XML DML, as shown.
-- the value.
UPDATE T
SET XmlCol.modify('
declare default element namespace "QNameXSD";
replace value of /Root[1]/ElemQN
with expanded-QName("https://myURI", "myLocalName") ')
go
-- Verify the result
SELECT * from T
go
This is the result. Note that the element <ElemQN> of QName type now has a new value:
<Root xmlns="QNameXSD" xmlns:ns="urn">
<ElemQN xmlns:p1="https://myURI">p1:myLocalName</ElemQN>
</Root>
The following statements remove the objects used in the example.
-- Cleanup
DROP TABLE T
go
drop xml schema collection SC
go
The expanded-QName function cannot be used in XML construction. The following example illustrates this. To work around this limitation, the example first inserts a node and then modifies the node.
-- if exists drop the table T
--drop table T
-- go
-- Create XML schema collection
-- DROP XML SCHEMA COLLECTION SC
-- go
CREATE XML SCHEMA COLLECTION SC AS '
<schema xmlns="http://www.w3.org/2001/XMLSchema">
<element name="root" type="QName" nillable="true"/>
</schema>'
go
-- Create table T with a typed xml column (using the XML schema collection)
CREATE TABLE T (xmlCol XML(SC))
go
-- Insert an XML instance.
insert into T values ('<root xmlns:a="https://someURI">a:b</root>')
go
-- Verify
SELECT *
FROM T
The following attempt adds another <root> element but fails, because the expanded-QName() function is not supported in XML construction.
update T SET xmlCol.modify('
insert <root>{expanded-QName("http://ns","someLocalName")}</root> as last into / ')
go
A solution to this is to first insert an instance with a value for the <root> element and then modify it. In this example, a nil initial value is used when the <root> element is inserted. The XML schema collection in this example allows a nil value for the <root> element.
update T SET xmlCol.modify('
insert <root xsi:nil="true"/> as last into / ')
go
-- now replace the nil value with another QName.
update T SET xmlCol.modify('
replace value of /root[last()] with expanded-QName("http://ns","someLocalName") ')
go
-- verify
SELECT * FROM T
go
-- result
<root>b</root>
<root xmlns:a="https://someURI">a:b</root>
<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p1="http://ns">p1:someLocalName</root>
You can compare the QName value, as shown in the following query. The query returns only the <root> elements whose values match the QName type value returned by the expanded-QName() function.
SELECT xmlCol.query('
for $i in /root
return
if ($i eq expanded-QName("http://ns","someLocalName") ) then
$i
else
()')
FROM T
There is one limitation: The expanded-QName() function accepts the empty sequence as the second argument and will return empty instead of raising a run-time error when the second argument is incorrect.