Question

我有一个表具有以下定义：

CREATE TABLE [dbo].[Due] (
[dueID]           INT            IDENTITY (1, 1) NOT NULL,
[dueTypeID]       INT            NOT NULL,
[vehicleID]        INT            NOT NULL,
[dueDate]         DATE           NULL,
...

这里我想生成一个输出为

的查询

VehicleID  Type1.dueDate  Type2.dueDate  Type3.dueDate ...

（截止日期应为该车型的最低日期）

我写了以下查询来执行此操作：

select vehicleNumber, A.dueDate, B.dueDate, C.dueDate, D.dueDate, E.dueDate, F.dueDate 
FROM Vehicle INNER JOIN 
(SELECT Max(dueDate) as dueDate,vehicleID from Due where dueTypeID = '1' GROUP BY Due.vehicleID) As A ON Vehicle.vehicleID = A.vehicleID INNER JOIN
(SELECT Max(dueDate) as dueDate,vehicleID from Due where dueTypeID = '2' GROUP BY Due.vehicleID) As B ON Vehicle.vehicleID = A.vehicleID INNER JOIN
(SELECT Max(dueDate) as dueDate,vehicleID from Due where dueTypeID = '3' GROUP BY Due.vehicleID) As C ON Vehicle.vehicleID = A.vehicleID INNER JOIN
(SELECT Max(dueDate) as dueDate,vehicleID from Due where dueTypeID = '4' GROUP BY Due.vehicleID) As D ON Vehicle.vehicleID = A.vehicleID INNER JOIN
(SELECT Max(dueDate) as dueDate,vehicleID from Due where dueTypeID = '5' GROUP BY Due.vehicleID) As E ON Vehicle.vehicleID = A.vehicleID INNER JOIN
(SELECT Max(dueDate) as dueDate,vehicleID from Due where dueTypeID = '6' GROUP BY Due.vehicleID) As F ON Vehicle.vehicleID = A.vehicleID

问题是，没有特定类型的到期日的车辆正在考虑其他车辆的价值。请帮我弄清楚如何解决这个问题，如果我这样做是正确的，或者是否有更好的方法来做到这一点？

（抱歉，如果问题重复，我尝试寻找它但找不到合适的关键字来搜索问题）

非常感谢帮助我。

Answer 1

试试这个：

 select vehicleNumber, 
     Max(case When dueTypeID = '1' Then dueDate Else null end) Typ1dueDate, 
     Max(case When dueTypeID = '2' Then dueDate Else null end) Typ2dueDate, 
     Max(case When dueTypeID = '3' Then dueDate Else null end) Typ3dueDate, 
     Max(case When dueTypeID = '4' Then dueDate Else null end) Typ4dueDate, 
     Max(case When dueTypeID = '5' Then dueDate Else null end) Typ5dueDate, 
     Max(case When dueTypeID = '6' Then dueDate Else null end) Typ6dueDate
 FROM Due d join Vehicle v 
     On v.vehicleId = d.vehicleId 
 Group By v.vehicleNumber

从同一个表的多行中选择列的值作为不同的列

1 个答案: