带有count和group by的SQL视图

Question

我有桌子Address,Property并且Listing:

Create Table Listing
    ( PropertyID int  -- Property ID as per the Property table
    , AgentID int
    , ListingDate DateTime not null property
    , AskingPrice Decimal(10,2) not null 
    , SaleDate Date
    , SalePrice Decimal(10, 2)  
    , Primary Key (PropertyID, ListingDate)
    , Foreign Key (PropertyID) references Property(PropertyID)
    , Foreign Key (AgentID) references Agent(AgentID) on delete no action on update no action

Create Table Address
    ( AddressID int Primary Key
    , StreetAddress varchar (100)
    , City varchar (50)
    , StateCode char(3)
    , PostalCode char (12)
    , Country varchar(30)
    )
        )
Create Table Property 
    ( PropertyID int Primary Key -- Unique ID for each property
    , AddressID int references Address(AddressID) On Delete no action on update no action
    , NumberOfRooms int not null Check (NumberOfRooms > 0) -- Number of rooms
    )

我想创建一个视图,其中包含每个城市的待售物业数量及其平均价格.物业是出售时AskingPrice,不是和SaleDate = null.问题是我无法得到每个城市的计数因为我得到错误

每个GROUP BY表达式必须至少包含一个不是外部引用的列

我该如何解决这个问题？

我的代码:

create view MarketStatistics as
select City = a.City,
     Properties = (select count(PropertyID)from Listing l where l.AskingPrice is not Null and l.SaleDate is Null group by a.City),
     AskingPrice = (select avg(AskingPrice)from Listing)
from Address a
join Property p on p.AddressID = a.AddressID
join Listing l on p.PropertyID = l.PropertyID

Answer 1

您的查询可以更加简单,只需在不使用子查询的情况下进行分组:

select 
    a.City,
    count(*) as Properties,
    avg(l.AskingPrice) as AskingPrice 
from Address a
inner join Property p on p.AddressID = a.AddressID
inner join Listing l on p.PropertyID = l.PropertyID
where l.AskingPrice is not Null and l.SaleDate is Null
group by a.City