Question

I have written a query which joins 3 tables where i need to inner join 2 tables and then inner join the whole result set with another join.

The query is as follows:

SELECT  R.ID,
        R.Title,
        R.Requirement_Text,
        R.Req_Owner,
        D.desname,
        D.team,
        D.stage,
        D.comm 
FROM Req R 
        LEFT JOIN 
        (
            SELECT  d1.ID AS 'id',
                    d1.designername AS 'desname',
                    d1.teamname AS 'team',
                    s.stage AS 'stage',
                    s.comments As 'comm' 
            FROM descomments d1 
                    LEFT JOIN stagecomments s ON d1.ID = s.ID 
                                                 AND d1.designername = s.designername
        ) D ON R.ID = D.id
WHERE R.ProjectID = 'STE 11.2' 
ORDER BY R.Priority

But i am getting following error:

com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: You have an error in your SQL syntax.  Check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT d1.ID AS 'id',d1.designername AS 'desname',d1.teamname A

Answer 1

You don’t need the ‘descomments’ after the first left join.. you’re actually joining to D, which is the result of your sub-join..

SELECT 
  R.ID,
  R.Title,
  R.Requirement_Text,
  R.Req_Owner,
  D.designername,
  D.teamname,
  s.stage,
  s.comments 
FROM Req R LEFT JOIN descomments D ON R.ID=D.id
LEFT JOIN stagecomments s ON D.ID=s.ID AND D.designername=s.designername
WHERE 
  R.ProjectID='STE 11.2' 
ORDER BY R.Priority