注意：

Question

我有两张桌子; hotelservices and guestorder

hotelservices

s_id(pk)    serviceType    serviceName

guestOrder表：

g_id(pk)    serviceType    totalAmount    balanceDue    PaidAmount    orderDate

我想根据hotelservice表中的serviceType获取totalAmount，balanceDue，PaidAmount的总和。

也就是说，它会迭代并对hotelservices.serviceType进行分组，并根据serviceType列从guestorder表中获取关联数据。

到目前为止我的尝试：

SELECT
 g.OrderDate as saleDate,
 g.ServiceType,
 sum(g.TotalAmount) as TotalSales,
 sum(g.BalanceDue) as TotalBalanceDue,
 sum(g.PaidAmount) as TotalPaid,
 h.ServicesType as services
 FROM guestorder as g join hotelservices as h on g.ServiceType=h.ServicesType
 group by saleDate

但这不是我想要的。我需要它来显示其他serviceType，即使它在guestorder中没有任何内容。我不知道我是否有意义。提前谢谢

Answer 1

也许反转你的联接，把它变成LEFT OUTER JOIN并用你的GROUP BY解决问题，例如：

SELECT
    g.OrderDate as saleDate,
    g.ServiceType,
    sum(g.TotalAmount) as TotalSales,
    sum(g.BalanceDue) as TotalBalanceDue,
    sum(g.PaidAmount) as TotalPaid,
    h.ServicesType as services
FROM 
    hotelservices as h 
    LEFT JOIN guestorder as g ON g.ServiceType=h.ServicesType
GROUP BY
    g.OrderDate,
    g.ServiceType,
    h.ServicesType;

Answer 2

i need it to show others serviceType even if it has nothing in the guestorder

从这个我假设您有不匹配的数据... 当你使用JOIN或INNER JOIN（因为那是JOIN默认的）时，你会过滤掉任何不匹配的东西。如果你想在没有过滤的情况下加入，那就做一个LEFT JOIN ..

你应该添加COALESCE（），这样就不会有像这样的NULL值

SELECT
    COALESCE(g.OrderDate, '') saleDate,
    COALESCE(g.ServiceType, '') guestServiceType,
    COALESCE(sum(g.TotalAmount), 0) TotalSales,
    COALESCE(sum(g.BalanceDue), 0) TotalBalanceDue,
    COALESCE(sum(g.PaidAmount), 0) TotalPaid,
    h.ServicesType as services
FROM hotelservices h 
LEFT JOIN guestorder g ON g.ServiceType = h.ServicesType
GROUP BY h.serviceType, saleDate

注意：

您的选择需要来自酒店服务表，以便您拥有所有服务类型..然后LEFT JOIN guestorder表，这样就没有过滤。

根据另一个表结果选择和分组

2 个答案:

注意：