sqldb2subqueryleft-join

DB2 - Using left join in a subquery


I managed to build a select that is working.

Now I need to JOIN to another table.

SELECT
    t.TICKETID -- the other table
    ,c.OWNERID 
    ,c.CREATEDATE
FROM 
    (
      SELECT 
        *
      , ROW_NUMBER () OVER (PARTITION BY c.OWNERID  ORDER BY c.CREATEDATE) AS RN_
      FROM  MAXIMO.COMMLOG c
      LEFT JOIN maximo.TICKET t  on t.TICKETUID  = c.OWNERID
      WHERE c.UNIQUEID = '468'
      AND c.OWNERID = '4355070'
    ) c
WHERE RN_ = 1
ORDER BY c.CREATEDATE DESC

Result without JOIN

OWNERID CREATEDATE
16031985 22022-08-11-08.02.30.351000

Expected result with JOIN

TICKETID OWNERID CREATEDATE
123456 16031985 2022-08-11-08.02.30.351000

Error for JOIN

Error SQL [42601]: An unexpected token "." was found following "c". Expected tokens may include: ",".. SQLCODE=-104, SQLSTATE=42601, DRIVER=4.31.10


Solution

  • Correlation names t and c of the subselect are not visible in the outer SELECT.
    You reuse c in outer and this is why you can use this correlation name to qualify the columns there.
    Try this.

    SELECT
         c.TICKETID -- Here is the information from the other table
        ,c.OWNERID 
        ,c.CREATEDATE
    
    FROM 
        (
          SELECT 
            c.*
          , t.TICKETID
          , ROW_NUMBER () OVER (PARTITION BY c.OWNERID  ORDER BY c.CREATEDATE) AS RN_
          FROM  MAXIMO.COMMLOG c
          left join maximo.TICKET t  on t.TICKETUID  = c.OWNERID -- here is my join
          WHERE c.UNIQUEID = '468'
          AND c.OWNERID = '4355070'
        ) c
    WHERE RN_ = 1
    ORDER BY c.CREATEDATE DESC