Linq to SQL 中是否提供 Unpivot(非 Pivot)功能?如何?

问题描述

我看过可以获取数据透视结果但不能获取数据透视结果的帖子，需要知道是否有任何干净的方法可以实现?如果不是，任何解决方法也可以吗?

I have seen posts which would fetch you pivot results but not unpivot, Need to know if there is any clean way to achieve ? If not the any workaround would do as well ?

执行此操作可在 Management Studio 中查看逆透视结果

Execute this to see unpivot results in Management Studio

CREATE TABLE [dbo].[Payment](
    [PaymentId] [int] NOT NULL,
    [EmployeeId] [int] NOT NULL,
    [RegularHours] [decimal](18, 0) NULL,
    [OvertimeHOurs] [decimal](18, 0) NULL
) ON [PRIMARY]

go

insert into payment values (1, 1, 40,  10)
insert into payment values (1, 2, 20,  0)

go

select * from payment 

select * from payment unpivot ([hours] for [paytype] in ([RegularHours], [OvertimeHOurs]))a

第一个 Select 语句的输出

The output for first Select statement

PaymentId   EmployeeId  RegularHours                            OvertimeHOurs
----------- ----------- --------------------------------------- 
1           1           40                                      10
1           2           20                                      0

(2 row(s) affected)

第二个 Select 语句的输出 &这就是我要找的

The output for second Select statement & this is what i am looking for

PaymentId   EmployeeId  hours                                   paytype
----------- ----------- ----------------------------------------------------- 
1           1           40                                      RegularHours
1           1           10                                      OvertimeHOurs
1           2           20                                      RegularHours
1           2           0                                       OvertimeHOurs

(4 row(s) affected)

推荐答案

好吧，我看不出有什么方法可以将它翻译成 SQL，下面是我想出的，但这都是执行的托管代码.

Ok, I cant see a way you can do it where it is translated into SQL, below is what I have come up with but this is all performed managed code.

或者...您可以简单地在 SQL 中创建一个视图.

Or... you can simply create a view in SQL.

var payments = Payments.Select (p => new {
                            OvertimeHOurs = new {
                                    p.PaymentId,
                                    p.EmployeeId,
                                    Hours = p.OvertimeHOurs,
                                    PayType = "OvertimeHOurs"
                                    },
                            RegularHours = new {
                                    p.PaymentId,
                                    p.EmployeeId,
                                    Hours = p.RegularHours,
                                    PayType = "RegularHours"
                                    }
                            }
                );
var result = payments.Select(a => a.OvertimeHOurs).Union(payments.Select (p => p.RegularHours));
result.Dump(); // LINQPad Method

生成的SQL是

-- Region Parameters
DECLARE @p0 NVarChar(1000) = 'OvertimeHOurs'
DECLARE @p1 NVarChar(1000) = 'RegularHours'
-- EndRegion
SELECT [t4].[PaymentId], [t4].[EmployeeId], [t4].[OvertimeHOurs] AS [Hours], [t4].[value] AS [PayType]
FROM (
    SELECT [t1].[PaymentId], [t1].[EmployeeId], [t1].[OvertimeHOurs], [t1].[value]
    FROM (
        SELECT [t0].[PaymentId], [t0].[EmployeeId], [t0].[OvertimeHOurs], @p0 AS [value]
        FROM [payment] AS [t0]
        ) AS [t1]
    UNION
    SELECT [t3].[PaymentId], [t3].[EmployeeId], [t3].[RegularHours], [t3].[value]
    FROM (
        SELECT [t2].[PaymentId], [t2].[EmployeeId], [t2].[RegularHours], @p1 AS [value]
        FROM [payment] AS [t2]
        ) AS [t3]
    ) AS [t4]