如何獲得Hibernate Query的ResultSet中的float值？

Question

我有以下查詢

select sum(r.score)/count(r) from Rating as r 
    group by r.item 
    order by sum(r.score)/count(r) desc 

我的問題是，休眠四捨五入的結果總和（r.score）/數（R）。

我該如何強制Hibernate返回結果的浮點值？

Answer 1

如果您只關心尋找平均值，那麼您可以使用avg()聚合函數，該函數始終返回Double。

select avg(r.score) from Rating as r 
    group by r.item 
    order by avg(r.score) desc 

Answer 2

avg最適合這種情況。對於一般情況下，你想轉換爲雙倍你可以使用CAST：

select sum(r.score)/(CAST (count(r) AS DOUBLE PRECISION)) from Rating as r 
    group by r.item 
    order by sum(r.score)/(CAST (count(r) AS DOUBLE PRECISION)) desc