DECLARE @x1 XML, @x2 XML, @x3 XML
SELECT @x1 = '<doc1></doc1><doc2></doc2>'
SELECT @x2 = '<doc3/>'
-- this is permitted by the spec
-- but produces an error in SQL Server
@SELECT @x3 = @x1 + @x2
-- this works
DECLARE @v1 VARCHAR(max)
SET @v1 = (CAST(@x1 AS VARCHAR(max))) + (CAST(@x2 AS VARCHAR(max)))
SET @x3 = @v1


-- Canonical mapping of a table in the ANSI spec -->
-- Also, it's the result of
SELECT * FROM EMPLOYEE
FOR XML RAW,ELEMENTS ROOT('EMPLOYEE') 

SELECT * FROM EMPLOYEE FOR XML AUTO,ELEMENTS