Question

以下是我的两张表：

CREATE TABLE Classes (
    Class_ID Varchar2(2) CONSTRAINT Classes_Class_ID_Pk PRIMARY KEY,
    Class_Name VARCHAR(15) CONSTRAINT Classes_Class_Name_NN NOT NULL,
    Price Number(5, 2),
    Start_Date DATE,
    End_Date DATE,
    Start_Time Varchar2(5),
    End_Time Varchar2(5),
    Day VARCHAR(10),
    Trainer_ID CONSTRAINT Classes_Trainer_ID_FK REFERENCES Trainers(Trainer_ID)
);

CREATE TABLE ClassSchedule (
    Class_ID Varchar2(2) CONSTRAINT Classes_Class_ID_FK REFERENCES Classes(Class_ID),
    Member_ID Varchar2(2) CONSTRAINT Members_Member_ID_FK REFERENCES Members(Member_ID),
    Paid CHAR(1),
    CONSTRAINT ClassSchedule_Combo_PK PRIMARY KEY (Class_ID, Member_ID)
);

现在，对于每个课程，我想列出课程ID，课程名称，每个班级的价格，每个班级的成员数量以及每个班级的总收入。我只想显示超过400美元的那些组，并按计算的总数对它们进行排序。这是我的查询不起作用：

SELECT
    C.Class_Id,
    Class_Name,
    Price,
    Count(S.Member_Id) AS Student_Count,
    (Student_Count * Price) AS Class_Revenue
FROM Classes C,
     ClassSchedule S
WHERE C.Class_ID = S.Class_Id
  AND (Student_Count * Price) > 400
ORDER BY Class_Revenue DESC

任何帮助将不胜感激。一直在撞墙试图让它发挥作用。

Answer 1

select Class_Id,Class_Name,Price,Student_Count*Price Class_Revenue from 
(Select 
C.Class_Id, 
Class_Name, 
Price, 
Count(S.Member_Id) As Student_Count
From Classes C, ClassSchedule S
Where C.Class_ID = S.Class_Id
group by C.Class_Id, 
Class_Name, 
Price
)
where having (Student_Count*Price) > 400
Order By Class_Revenue Desc;

Answer 2

尝试在over上使用count()子句：

select Class_Id, 
       Class_Name,
       Price,
       Student_Count,
       (Student_Count * Price) AS Class_Revenue
from
(SELECT
    C.Class_Id,
    Class_Name,
    Price,
    Count(S.Member_Id) over (partition by C.Class_Id) AS Student_Count
FROM Classes C,
     ClassSchedule S
WHERE C.Class_ID = S.Class_Id) t
where (Student_Count * Price) > 400
order by (Student_Count * Price) desc

查询两个表可能是一个联合

2 个答案: