How to use the & character in T-SQL's XML type?

Question

When I run:

SELECT name + '&' 
FROM sys.databases 
FOR XML PATH('');

The code returns this:

master&tempdb&model&msdb&

What I really want is:

master&tempdb&model&msdb&

I also tried:

SELECT name + CHAR(38) 
FROM sys.databases 
FOR XML PATH(''); 

This doesn't work, too. How can I get the expected result in the first place?

Without something like:

REPLACE(CAST('master&amp...l&msdb&' AS NVARCHAR(MAX)), '&', '&')

Answer 1

The FOR XML clause returns text by default so the result string includes XML predefined entity references, such as & for an ampersand, to represent special characters within the XML.

To avoid entity references in the result, include TYPE in the FOR XML clause to return the value as strongly-typed XML instead of text, which allows invocation of a value method on the XML node to get the value as nvarchar(MAX) without the entity references:

SELECT (
    SELECT name + '&'
    FROM sys.databases
    FOR XML PATH(''), TYPE
    ).value('(./text())[1]', 'nvarchar(MAX)');

The above example includes a trailing ampersand like your original query. One way to avoid the extraneous delimiter is with STUFF . Below is another example that prepends the delimiter to each value and removes the unneeded first one. Also, the singleton node value (./text())[1] specification will improve performance, a consideration for larger queries.

SELECT STUFF((
    SELECT '&' + name
    FROM sys.databases
    FOR XML PATH(''), TYPE
    ).value('(./text())[1]', 'nvarchar(MAX)'), 1, 1, '');

I'll add that you can avoid the XML ugliness for aggregate string concatenation in SQL Server 2017+ and Azure SQL Database using a much cleaner and less verbose STRING_AGG technique:

SELECT STRING_AGG(name, '&')
FROM sys.databases;

See this answer for a more detailed description of string aggegation using FOR XML .