sql - SQL-使用JOINS从三个表中获取值

Question

我在我的项目中使用了四个表，分别是 VehicleMaster、OwnerMaster、CustomerMaster 和 CustomerVehicle

顾名思义，前三个是主表，最后一个表 (CustomerVehicle) 包含 CustomerID 和 VehicleID。表层次结构如下

 OwnerMaster (OwnerID, OwnerName) 
 VehicleMaster (VehicleID, OwnerID, VehicleDetails blah blah...) 
 CustomerMaster (CustomerID, CustomerName..) 
 CustomerVehicle     (CustomerID, VehicleID)

现在我想知道每个车主有多少辆车在运行。输出应该是这样的。

OwnerName, TotalVehicles, No of Running Vehicles, NonRunning Vehicles.
xxxx, 40, 34, 6

任何帮助都感激不尽。谢谢，

Answer 1

像这样的东西应该有效；左加入表格并（不同）计算各个字段；

SELECT om.OwnerName, 
       COUNT(DISTINCT vm.VehicleID) TotalVehicles, 
       COUNT(DISTINCT cv.VehicleID) Running, 
       COUNT(DISTINCT vm.VehicleID)-COUNT(DISTINCT cv.VehicleID) NotRunning
FROM OwnerMaster om
LEFT JOIN VehicleMaster vm ON om.OwnerID = vm.OwnerID
LEFT JOIN CustomerVehicle cv ON vm.VehicleID = cv.VehicleID
GROUP BY om.OwnerID, om.OwnerName

一个用于测试的 SQLfiddle。

Answer 2

可能有没有车辆的车主，我们不知道......这样的事情也应该起作用：

SELECT 
  om.OwnerName,
  count(vm.VehicleID) Total,
  sum(case when vm.VehicleID is not null 
            and cv.VehicleID is not null then 1 else 0 end) Runnng,
  sum(case when vm.VehicleID is not null 
            and cv.VehicleID is null then 1 else 0 end) NotRunnng
FROM OwnerMaster om
LEFT JOIN VehicleMaster vm ON om.OwnerID = vm.OwnerID
LEFT JOIN CustomerVehicle cv ON vm.VehicleID = cv.VehicleID
GROUP BY om.OwnerName

Answer 3

非常感谢Elhana。我已经更新了我的查询以获得我需要的确切结果。修改查询为：

    SELECT 
    om.OwnerName,
    count(vm.VehicleID) Total,
    sum(case when vm.VehicleID is not null 
        and cv.VehicleID is not null then 1 else 0 end) Runnng,
     sum(case when vm.VehicleID is not null 
        and cv.VehicleID is null then 1 else 0 end) NotRunnng
    FROM OwnerMaster om
    LEFT JOIN VehicleMaster vm ON om.OwnerID = vm.OwnerID and vm.isactive = 1
    LEFT JOIN (select distinct VehicleID from CustomerVehicle where isactive = 1) cv
    ON vm.VehicleID = cv.VehicleID
    where om.isactive = 1
    GROUP BY om.OwnerName

SQL小提琴