從分組列中選擇最大值的Sql問題

Question

嗨，大家好，我真的有問題。

select * from Insurance_Plan; 
    select * from Enroll; 
    select * from Patient; 

這三個是我的數據庫中的表。現在我必須爲患者最多的參與者獲得保險計劃，併爲此計劃，名​​稱，所需的共付金額以及患者登記人數。

我已經做了部分到這裏：

Select I.Insurance_Name,Max(I.Insurance_Copayment_Amount) As 
    Copayment_Amount,count(P.Patient_ID) As Number_Of_Patients 
    From Insurance_Plan as I inner Join 
    Enroll AS E on I.Insurance_Plan_ID=E.Insurance_Plan_ID 
    inner join Patient as P on P.Patient_ID=E.Patient_ID 
    group by Insurance_Name 

其結果是我得到的輸出：

現在我想只顯示與入選的患者最大數量的保險計劃，是顯示的輸出中的第二行。我正在嘗試使用Max函數，但遇到錯誤。它必須在一個有效的查詢中完成。

Answer 1

Select top (1) I.Insurance_Name,Max(I.Insurance_Copayment_Amount) As 
    Copayment_Amount,count(P.Patient_ID) As Number_Of_Patients 
    From Insurance_Plan as I inner Join 
    Enroll AS E on I.Insurance_Plan_ID=E.Insurance_Plan_ID 
    inner join Patient as P on P.Patient_ID=E.Patient_ID 
    group by Insurance_Name 
    order by count(P.Patient_ID) desc 

Answer 2

嘗試在查詢的末尾添加

having Max(Number_Of_Patients) = Number_Of_Patients 

。

Here you will find a good example for having-max.