德比数据库中限制记录组的sql

Question

我只想在 derby 数据库中检索十条记录。我一直在搜索教程：

select * from (select  ROW_NUMBER() OVER() AS rownum,name,effort from (select  name, effort from
(select TBL_PROJECT_DETAIL.P_NAME as Name, sum(TBL_TIMESHEET.EFFORT) as effort from
TBL_TIMESHEET join tbl_project_detail on TBL_TIMESHEET.PROJECT_ID = TBL_PROJECT_DETAIL.ID group by TBL_PROJECT_DETAIL.P_NAME) as New)
as new2)
as new3 
where rownum <= 10

我可以先使用 where rownum <= 10 最后将数据限制为 10，但问题是数据不是首先使用 order by 子句排序的，所以我得到了 10 个随机数据。

当我把order by 放在数据之前给rownum:

select * from (select  ROW_NUMBER() OVER() AS rownum,name,effort from 
(select  name, effort from
(select TBL_PROJECT_DETAIL.P_NAME as Name, sum(TBL_TIMESHEET.EFFORT) as effort from
TBL_TIMESHEET join tbl_project_detail on TBL_TIMESHEET.PROJECT_ID = TBL_PROJECT_DETAIL.ID group by TBL_PROJECT_DETAIL.P_NAME)
as New)
as new2 order by effot desc)
as new3  where rownum <=10

它给出了错误。就像不能group by当你把结果作为内表再次查询时一样，但是对derby的要求是使用row_number。首先在内部添加 row_number 并在下一层中使用它。任何人都可以帮忙吗？德比不受支持限制。有什么其他方法可以让我先订购 10 条记录吗？

Answer 1

我一直在研究，发现是这样的 使用

限制德比

FETCH FIRST 10 ROWS ONLY

但可怜的我支持 derby 10.5 并且我正在使用 derby 10.4 捆绑包和 glassfish 2.1 如果我仍然使用 10.4，任何人都可以提供帮助，因为我太害怕迁移了

Answer 2

您可以在“OVER()”中给出 order by 子句

OVER(order by effot desc) AS rownum