How to concatenate multiple rows?

Question

I have the following query which returns the salary of all employees. This work perfectly but I need to collect extra data that I will aggregate into one cell (see Result Set 2).

How can I aggregate data into a comma separated list? A little bit like what Sum does, but I need a string in return.

SELECT Employee.Id, SUM(Pay) as Salary
FROM Employee
INNER JOIN PayCheck ON PayCheck.EmployeeId = Employee.Id
GROUP BY Employee.Id

Result Set 1

Employee.Id              Salary
-----------------------------------
          1                 150
          2                 250
          3                 350

I need:

Result Set 2

Employee.Id              Salary                 Data
----------------------------------------------------
          1                 150      One, Two, Three
          2                 250      Four, Five, Six
          3                 350      Seven

possible duplicate of [How do I Create a Comma-Separated List using a SQL Query?](http://stackoverflow.com/questions/1817985/how-do-i-create-a-comma-separated-list-using-a-sql-query) and of http://stackoverflow.com/questions/3087684/sql-query-to-return-values-of-a-particular-column-concactenated-with-comma/3087799#3087799 @Martin this last one has a better example of using it in a 'GROUP BY' There is also an option of using a custom CLR aggregate. — Martin Smith, Jun 25 '10 at 20:05
Maybe I missed something here, but where are you getting the extra data from? — VoodooChild, Jun 25 '10 at 20:06
SqlServer 2017 now has STRING_AGG that aggregates multiple strings into one using a given separator. (Not allowed to post a duplicate answer to a duplicate question.) — John, Aug 31 '17 at 11:19

OMG Ponies · Accepted Answer · 2011-02-17T16:26:07.487

3

For SQL Server 2005+, use the STUFF function and FOR XML PATH:

WITH summary_cte AS (
   SELECT Employee.Id, SUM(Pay) as Salary
     FROM Employee
     JOIN PayCheck ON PayCheck.EmployeeId = Employee.Id
 GROUP BY Employee.Id)
SELECT sc.id, 
       sc.salary,
       STUFF((SELECT ','+ yt.data
                FROM your_table yt
               WHERE yt.id = sc.id
            GROUP BY yt.data
             FOR XML PATH(''), TYPE).value('.','VARCHAR(max)'), 1, 1, '')
  FROM summary_cte sc

But you're missing details about where the data you want to turn into a comma delimited string is, and how it relates to an employee record...

edited Feb 17 '11 at 16:26

answered Jun 25 '10 at 20:18

OMG Ponies

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this does not properly handle XML special characters like `>` and `&`. So if your_table.data contained `one & two` you'd get `one & two` in the result set. There is a nifty way to handle this, see: http://stackoverflow.com/questions/5031204/does-t-sql-have-an-aggregate-function-to-concatenate-strings/5031297#5031297 – KM. Feb 17 '11 at 16:23

score 0 · Answer 2 · answered Jun 25 '10 at 20:08

I don't have my code in front of me, or I would show you a quick example, but I would look into writing a CLR aggregate for this. Its very simple. There are some automatically created method to use, and they're just for collection (add to a List<> object or something), Merge (merging multiple lists created in multiple threads), and an output (take the list and turn it into a string - String.Join(",", list.ToArray())). Only thing to know is that there is a length limit of 8000 characters.

How to concatenate multiple rows?

2 Answers2

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