Question

我的查询以：

结尾

GROUP BY supervisor,
     agent,
     task
ORDER BY supervisor,
     agent,
     'task_count'

我遇到的是每个代理可以拥有超过100个任务，而且我只希望列出每个代理的前20个（通过task_count）。如果我使用LIMIT，则会将整个结果列表限制为20.是否有办法只将LIMIT应用于代理列？谢谢！

Answer 1

不，你可以使用row_number()：

select . . . 
from (select t.*,
             row_number() over (partition by agent order by task_count desc) as seqnum
      from t
     ) t
where seqnum <= 20;

如果正在计算task_count，请执行以下操作：

select t.*
from (select t.agent, t.task, count(*) as task_count,
             row_number() over (partition by agent order by count(*) desc) as seqnum
      from t
      group by t.agent, t.task
     ) t
where seqnum <= 20;

Answer 2

不确定您的平台，但在DB2上它看起来像这样：

select -- stuff
  supervisor, agent, ordn
from (
  SELECT -- stuff
     supervisor, agent,
     row_number() over (partition by supervisor, agent order by count(*) RANGE   BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) as ordn
  GROUP BY supervisor, agent
) x
where ordn <= 20
order by  supervisor, agent, ordn

请注意，您需要范围，因为默认情况下，范围是当前的和无限制的。

Impala SQL按列限制

2 个答案: