Concatenate row values T-SQL

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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!

concatenation tsql sql-server sql
15 Answers

Turns out there is an even easier way to do this which doesn't require a UDF:

select replace(replace(replace((cast((
        select distinct columnName as X
        from tableName 
        for xml path('')) as varchar(max))), 
   '</X><X>', ', '),'<X>', ''),'</X>','')
user_2614380

Now from SQL server 2017 there is a new T-SQL function called STRING_AGG:
it is a new aggregate function that concatenates the values of string expressions and places separator values between them.
The separator is not added at the end of string.

Example: 

SELECT STRING_AGG ( ISNULL(FirstName,'N/A'), ',') AS csv 
FROM Person.Person;

the result set:

John,N/A,Mike,Peter,N/A,N/A,Alice,Bob
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