How to concatenate strings from multiple rows in one column + inner join in one query

Question

I have a query with the following result: query:

SELECT Tasks.TaskId, Comments.Comment, comments.timespent       
FROM   comments
INNER JOIN tasks ON commen         


        

Answer 1

Ok, this is a bit more complicated but it doesn't use xml, and it can be used with other databases than sql server:

    WITH orig
         AS (SELECT 1 AS f1, 'C11' AS f2
             UNION ALL
             SELECT 1 AS f1, 'C12' AS f2
             UNION ALL
             SELECT 1 AS f1, 'C13' AS f2
             UNION ALL
             SELECT 2 AS f1, 'C21' AS f2
             UNION ALL
             SELECT 2 AS f1, 'C22' AS f2
             UNION ALL
             SELECT 2 AS f1, 'C23' AS f2
             UNION ALL
             SELECT 3 AS f1, 'C31' AS f2)
       , orig2 AS (SELECT DISTINCT f1, f2 FROM orig)
       , orig3 AS (SELECT f1, f2, row_number() OVER(PARTITION BY f1 ORDER BY f2) AS RowNum FROM orig2)
       , orig4
         -- Use recursion to concatenate the fields
         AS (SELECT f1, CONVERT(VARCHAR(MAX), f2) AS val, rownum
               FROM orig3
              WHERE RowNum = 1
             UNION ALL
             SELECT orig4.f1, orig4.val + ', ' + orig3.f2 AS val, orig3.rownum
               FROM orig4
                    INNER JOIN orig3
                      ON orig4.RowNum + 1 = orig3.RowNum
                     AND orig4.f1 = orig3.f1)
    SELECT *
      FROM orig4
     -- select only the rows that match the maximum rownum
     WHERE NOT EXISTS
             (SELECT 1
                FROM orig4 o44
               WHERE o44.f1 = orig4.f1
                 AND o44.rownum > orig4.rownum)

Another approach that works only for sql server would be to build an aggregate CLR function that concatenates the values: http://msdn.microsoft.com/en-us/library/91e6taax%28v=vs.90%29.aspx.

If you came across this article but you use oracle, you have the option to use the query above or define a custom aggregate function in pl/sql (http://docs.oracle.com/cd/B28359_01/appdev.111/b28425/aggr_functions.htm).