The Coalesce function can be used to produce that result. Coalesce returns the first non null value in a set. If you use it in the following manner it will recursivly return each value in order until it nulls out and return it as a comma delimited string. You can use any other delimiter if you want.
DECLARE @pAddr VarChar(MAX)
SELECT @pAddr = COALESCE(@pAddr + ', ', '') + [Address]
FROM AddressTable
WHERE AddressTable.Key = @pKey
You could put this code into a UDF, and then in a view simply call that UDF passing the key.
