Use ampersand in CAST in SQL - sql

Question

The following code snippet on SQL server 2005 fails on the ampersand '&':
select cast('<name>Spolsky & Atwood</name>' as xml)
Does anyone know a workaround?
Longer explanation, I need to update some data in an XML column, and I'm using a search & replace type hack by casting the XML value to a varchar, doing the replace and updating the XML column with this cast.

Answer 1

select cast('<name>Spolsky & Atwood</name>' as xml)
A literal ampersand inside an XML tag is not allowed by the XML standard, and such a document will fail to parse by any XML parser.
An XMLSerializer() will output the ampersand HTML-encoded.
The following code:
using System.Xml.Serialization;
namespace xml
{
public class MyData
{
public string name = "Spolsky & Atwood";
}
class Program
{
static void Main(string[] args)
{
new XmlSerializer(typeof(MyData)).Serialize(System.Console.Out, new MyData());
}
}
}
will output the following:
<?xml version="1.0" encoding="utf-8"?>
<MyData
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<name>Spolsky & Atwood</name>
</MyData>
, with an & instead of &.

Answer 2

It's not valid XML. Use &:
select cast('<name>Spolsky & Atwood</name>' as xml)

Answer 3

You'd need to XML escape the text, too.
So let's backtrack and assume you're building that string as:
SELECT '<name>' + MyColumn + '</name>' FROM MyTable
you'd want to do something more like:
SELECT '<name>' + REPLACE( MyColumn, '&', '&' ) + '</name>' FROM MyTable
Of course, you probable should cater for the other entities thus:
SELECT '<name>' + REPLACE( REPLACE( REPLACE( REPLACE( REPLACE( MyColumn, '&', '&' ), '''', '&apos;' ), '"', '"' ), '<', '<' ), '>', '>' ) + '</name>' FROM MyTable

Answer 4

When working with XML in SQL you're a lot safer using built-in functions instead of converting it manually.
The following code will build a proper SQL XML variable that looks like your desired output based on a raw string:
DECLARE #ExampleString nvarchar(40)
, #ExampleXml xml
SELECT #ExampleString = N'Spolsky & Atwood'
SELECT #ExampleXml =
(
SELECT 'Spolsky & Atwood' AS 'name'
FOR XML PATH (''), TYPE
)
SELECT #ExampleString , #ExampleXml

Answer 5

As John and Quassnoi state, & on it's own is not valid. This is because the ampersand character is the start of a character entity - used to specify characters that cannot be represented literally. There are two forms of entity - one specifies the character by name (e.g., &, or "), and one the specifies the character by it's code (I believe it's the code position within the Unicode character set, but not sure. e.g., " should represent a double quote).
Thus, to include a literal & in a HTML document, you must specify it's entity: &. Other common ones you may encounter are < for <, > for >, and " for ".