Concatenate row values T-SQL

Question

I am trying to pull together some data for a report and need to concatenate the row values 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;

Can anyone give me a hand with this? Any help would be greatly appreciated!

Answer 1

When the number of items is small this can be done using ROW_NUMBER() OVER PARTITION BY:

declare @t table (col1 int, col2 varchar)
insert into @t VALUES (1,'A')
insert into @t VALUES (1,'B')
insert into @t VALUES (1,'C')
insert into @t VALUES (1,'D')
insert into @t VALUES (1,'E')
insert into @t VALUES (2,'X')
insert into @t VALUES (3,'Y')

select col1,
    MAX(CASE seq WHEN 1 THEN        col2 ELSE '' END ) + 
    MAX(CASE seq WHEN 2 THEN ', ' + col2 ELSE '' END ) + 
    MAX(CASE seq WHEN 3 THEN ', ' + col2 ELSE '' END ) +
    MAX(CASE seq WHEN 4 THEN ', ' + col2 ELSE '' END ) +
    MAX(CASE seq WHEN 5 THEN ',...' ELSE '' END ) 
    as col2
from (
    select col1, col2, ROW_NUMBER() OVER ( PARTITION BY col1 ORDER BY col2 ) seq
    from @t
    group by col1, col2
) x
group by col1

Answer 2

Had similar problem and found a sweet solution after playing with code for 15 minutes

declare @result varchar(1000)
select @result = COALESCE(@result+','+A.col1, A.col1)
                FROM (  select  col1
                        from [table] 
                ) A
select @result

Returns result as value1,value2,value3,value4

Enjoy ;)

Answer 3

Select R.ReviewID, ReviewDate
, (Select  FName + ', ' 
   from Users 
   where UserID = R.UserID 
   order by FName FOR XML PATH(')
) as [Users]
from Reviews
inner join Reviewers AS R
  On Reviews.ReviewID = R.ReviewID
Group By R.ReviewID, ReviewDate;