PostgreSQL:只从包含多行的结果中获取一条记录

 SELECT t.taskid AS id,
    t.projectid AS project,
    te.effort AS effort,
    (((t.taskname::text || ' | '::text) || m.milestonename::text) || ' | '::text) || p.projectname::text AS name,
    t.status,
    1 AS version
   FROM task t
     LEFT JOIN timeentry te ON t.taskid = te.taskid
     LEFT JOIN project p ON t.projectid = p.projectid
     LEFT JOIN milestonetask tm ON t.taskid = tm.taskid
     FULL JOIN milestone m ON tm.milestoneid = m.milestoneid
  WHERE m.milestoneid IS NOT NULL
UNION
 SELECT distinct(t.taskid) AS id,
    t.projectid AS project,
    te.effort AS effort,
    (t.taskname::text || ' | (--no milestone--) | '::text) || p.projectname::text AS name,
    t.status,
    1 AS version
  FROM task t 
     LEFT JOIN timeentry te ON t.taskid = te.taskid
     LEFT JOIN project p ON t.projectid = p.projectid
     LEFT JOIN milestonetask tm ON t.taskid = tm.taskid
     FULL JOIN milestone m ON tm.milestoneid = m.milestoneid
  WHERE NOT (tm.taskid IN ( SELECT DISTINCT milestonetask.taskid
           FROM milestonetask
          WHERE milestonetask.milestoneid IS NOT NULL));

id | project | effort |        name       | status | version 
----+---------+--------+------------------+--------+---------
 89 |       1 |      5 | Coding for clock | Active |       1
 89 |       1 |      2 | Coding for clock | Active |       1
 89 |       1 |      4 | Coding for clock | Active |       1

请告诉我,如果我足够清楚,将非常感谢您的帮助和提前感谢。