Select multiple rows into one variable in SQL Query

Question

SELECT ft.ThreadTitle AS Title, 
fr.ReplyText + ' ' + ua2.Username + ' ' + ft.ThreadText + ' '  +

-- THIS NEXT LINE IS WHAT I WANT TO ACHIEVE:

(Select ReplyText from ForumReply Where ThreadID=ft.ThreadID) 

-- THE ABOVE LINE HAVE MULTIPLE ROWS/VALUES THAT I WANT TO JOIN INTO ONE VARIABLE. HOW?
AS [Content], 

ss.Domain, 
ss.SiteID, 
ft.ThreadID AS ObjectId
FROM         dbo.ForumReply AS fr INNER JOIN
                      dbo.ForumThreads AS ft ON fr.ThreadID = ft.ThreadID INNER JOIN
                      dbo.User_Account AS ua1 ON ft.CreateByUserID = ua1.UserID INNER JOIN
                      dbo.User_Account AS ua2 ON fr.ReplyUserID = ua2.UserID INNER JOIN
                      dbo.SysT_Site AS ss ON ua1.SiteID = ss.SiteID

This query gives error: Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

How do I rewrite this query to work so that I get all the values into one variable? The end result need to be a "View" that looks like this:

.ObjectID int

.Content (string with all text that exists in the Forumthread.threadText and forumReply.ReplyText)

.Domain string

.SiteID int

Answer 1

Building upon Martin's comment:

DECLARE @t TABLE  (id int, ReplyText varchar(100))
INSERT INTO @t (id, ReplyText) VALUES (1, 'So Long,')
INSERT INTO @t (id, ReplyText) VALUES  (2, 'And Thanks for')
INSERT INTO @t (id, ReplyText) VALUES  (3, 'All the Fish!')

SELECT (SELECT replytext + ' '  FROM @t FOR XML PATH('')) AS CONTENT

Answer 2

You can assign to local variable this way.

SELECT @TempVariable = (SELECT replytext + ' ' FROM @t FOR XML PATH(''))

Answer 3

What you need is a string concat aggregate function, which sql server unfortunuatley does not include.

You can create your own though using .Net CLr function see here and here