SQL: how to get all the distinct characters in a column, across all rows

Question

Is there an elegant way in SQL Server to find all the distinct characters in a single varchar(50) column, across all rows?

Bonus points if it can be done without cur

Answer 1

Building on mdma's answer, this version gives you a single string, but decodes some of the changes that FOR XML will make, like & -> &.

WITH ProductChars(aChar, remain) AS (
   SELECT LEFT(productName,1), RIGHT(productName, LEN(productName)-1) 
      FROM Products WHERE LEN(productName)>0
   UNION ALL
   SELECT LEFT(remain,1), RIGHT(remain, LEN(remain)-1) FROM ProductChars
      WHERE LEN(remain)>0
)
SELECT STUFF((
  SELECT N'' + aChar AS [text()]
  FROM (SELECT DISTINCT aChar FROM Chars) base
  ORDER BY aChar
FOR XML PATH, TYPE).value(N'.[1]', N'nvarchar(max)'),1, 1, N'')
-- Allow for a lot of recursion. Set to 0 for infinite recursion
OPTION (MAXRECURSION 365)