How can I group fields from multiple records in T-SQL by another field?

Question

I am trying to concatenate rows of one of the tables. Here is the basic table structure:

Reviews

 ReviewID  
 ReviewDate  

Reviewers

 ReviewerID  
 ReviewID  
 UserID  

Users

UserID  
FName  
LName  

This is a M:M relationship. Each Review can have many Reviewers; each User can be associated with many Reviews.

Basically, all I want to see is Reviews.ReviewID, Reviews.ReviewDate, and a concatenated string of the FName's of all the associated Users for that Review (comma delimited).

Instead of:

ReviewID---ReviewDate---User  
1----------12/1/2009----Bob  
1----------12/1/2009----Joe  
1----------12/1/2009----Frank  
2----------12/9/2009----Sue  
2----------12/9/2009----Alice  

Display this:

ReviewID---ReviewDate----Users  
1----------12/1/2009-----Bob, Joe, Frank  
2----------12/9/2009-----Sue, Alice

I have found this article describing some ways to do this, but most of these seem to only deal with one table, not multiple; unfortunately, my SQL-fu is not strong enough to adapt these to my circumstances. I am particularly interested in the example on that site which utilizes FOR XML PATH() as that looks the cleanest and most straight forward.

SELECT p1.CategoryId,
( SELECT ProductName + ', '
  FROM Northwind.dbo.Products p2
  WHERE p2.CategoryId = p1.CategoryId
  ORDER BY ProductName FOR XML PATH('')
) AS Products
FROM Northwind.dbo.Products p1
GROUP BY CategoryId;

Answer 1

Have a look at this

DECLARE @Reviews TABLE(
        ReviewID INT,
        ReviewDate DATETIME
)

DECLARE @Reviewers TABLE(
        ReviewerID   INT,
        ReviewID   INT,
        UserID INT
)

DECLARE @Users TABLE(
        UserID  INT,
        FName  VARCHAR(50),
        LName VARCHAR(50)
)

INSERT INTO @Reviews SELECT 1, '12 Jan 2009'
INSERT INTO @Reviews SELECT 2, '25 Jan 2009'

INSERT INTO @Users SELECT 1, 'Bob', ''
INSERT INTO @Users SELECT 2, 'Joe', ''
INSERT INTO @Users SELECT 3, 'Frank', ''
INSERT INTO @Users SELECT 4, 'Sue', ''
INSERT INTO @Users SELECT 5, 'Alice', ''

INSERT INTO @Reviewers SELECT 1, 1, 1
INSERT INTO @Reviewers SELECT 2, 1, 2
INSERT INTO @Reviewers SELECT 3, 1, 3
INSERT INTO @Reviewers SELECT 4, 2, 4
INSERT INTO @Reviewers SELECT 5, 2, 5

SELECT  *,
        ( 
            SELECT  u.FName + ','
            FROM    @Users u INNER JOIN 
                    @Reviewers rs ON u.UserID = rs.UserID
            WHERE   rs.ReviewID = r.ReviewID
            FOR XML PATH('')
        ) AS Products
FROM    @Reviews r