Question

伙计我有以下问题：

select count(*) AS num_items
       from desc_look
       group by dept

此查询返回每个部门中的项目数。但是，我不能只获得物品数量较多的部门。

我一直试图用它来检索大部分项目的部门名称和ID

select dept, desc_up
from desc_look
where (select count(*) AS num_items
       from desc_look
       group by dept)

但是我一直收到错误ORA-00936而且我不知道为什么。我知道我不能使用MAX（COUNT（*））但是有办法解决这个问题吗？

Answer 1

select * from
(
    select count(*) AS num_items
    from desc_look
    group by dept
    order by count(*) desc
) tmp
WHERE ROWNUM = 1;

另请查看howto limit the records in Oracle。

Answer 2

此版本与juergen的版本基本相同，但使用分析函数而不是聚合（GROUP BY）进行计数：

SELECT t.dept, t.desc_up FROM
  (SELECT dept, desc_up,
   COUNT(*) over (partition BY dept) dept_count
   FROM desc_look
   ORDER BY dept_count DESC
  ) t
WHERE rownum = 1

如果您使用的是Oracle 12，则不需要内联视图，因为您可以使用行限制子句（FETCH FIRST ...）：

SELECT dept, desc_up,
  COUNT(*) over (partition BY dept) dept_count
FROM desc_look
ORDER BY dept_count DESC
FETCH FIRST 1 ROW ONLY

Answer 3

我认为这可能会对你有所帮助

select count(*) AS num_items
       from desc_look
       group by dept
       order by count(*) desc
       limit 1

Answer 4

您可以尝试这样的事情：

SELECT dept, num_items FROM (
    SELECT dept, COUNT(*) AS num_items
         , ROW_NUMBER() OVER ( ORDER BY COUNT(*) DESC ) AS rn
      FROM desc_look
     GROUP BY dept
) WHERE rn = 1;

查询获取“MAX COUNT”

4 个答案: