Question

(I’m using Oracle and JPA (from Java EE 5, WebSphere 7)).

I have a Project class, Project has a list of Tasks.

Each Task has a sequence number so I can determine the task’s sequential order (Task.seq), and a assigned user (Task.userId), and a String status Task.status (“IN_PROGRESS” or “COMPELTE”). The tasks for a project get “COMPLETED” by their assigned user in their numerical sequence.

My problem is … this is the tricky bit … I need a query that does the following:

Given a userid, find all Projects where the current task of that project is assigned to the user. (The ‘current task’ is the first task found in numerical sequence that has a status of “IN_PROGRESS”.)

I’m not great with SQL, and pretty new to JPA — please help!

PS. For example, here’s the query I’m currently using that gets me all Project objects with the task list populated:

select distinct p from Project p left join fetch p.taskList

Any help is greatly appreciated!

Rob

Answer 1

To think about this, start by finding the first task for the user. Then, join in the project information, and select whatever you want to know about the projects:

select distinct p.*
from (select userid, projectid, min(t.seq) as firstseq
      from Task t
      where t.userid = <userid> and 
            t.status = 'IN PROGRESS'
      group by userid, projectid
     ) u join
     Task t
     on t.projectid = u.projectid and
        t.seq = u.firstseq join
     Project p
     on p.projectid = u.projectid

I’m assuming the task has a projectid, although you don’t explicitly say that.

This solution should work in just about any database.