Question

我有以下要转换为LinqToSql

的SQL查询

SELECT recWishList.AppId, phyDM.Name,
DATEADD(dd, DATEDIFF(dd, 0, recWishList.Timestamp), 0) AS Date,
COUNT(recWishList.Timestamp) AS Downloads
FROM 
dbo.RecommendWishlist recWishList
INNER JOIN VirtualDevice virDevice
on recWishList.VirtualDeviceId = virDevice.Id
INNER JOIN PhysicalDeviceModel phyDM
on virDevice.PhysicalDeviceModelId = phyDM.Id
GROUP BY 
AppId, phyDM.Name, DATEADD(dd, DATEDIFF(dd, 0, recWishList.Timestamp), 0)

上面的Date列计算是一个hack，通常用于从datetime值中剥离时间组件，实质上是将时间组件设置为零。

结果结果集如下所示：

AppId                                   Model           Date                  Downloads
0219d640-6e56-4c09-be8a-a4dc4777bf31    M1           2010-08-30 00:00:00.000 1
04d2de8b-646f-4433-8738-76103344e6b2    M2           2010-12-06 00:00:00.000 1
07d09852e9ca439cb0c573c8292e64f5     M2           2010-08-25 00:00:00.000 1
07d09852e9ca439cb0c573c8292e64f5     M2           2010-09-13 00:00:00.000 1
07d09852e9ca439cb0c573c8292e64f5     M1           2010-08-25 00:00:00.000 2

我的L2S等价物如下：

from app in RecommendWishlists
join virtualDevice in VirtualDevices on app.VirtualDeviceId equals virtualDevice.Id
join physicalDeviceModel in PhysicalDeviceModels on virtualDevice.PhysicalDeviceModelId       equals physicalDeviceModel.Id
group app by new {app.AppId, Model=physicalDeviceModel.Name, Date =    SqlMethods.DateDiffDay(DateTime.Parse("1/1/1753"),app.Timestamp)} into gApp
select new {App = gApp.Key.AppId, Model = gApp.Key.Model, Date = gApp.Key.Date}

结果集如下所示：

AppId                                   Model           Date                    
0219d640-6e56-4c09-be8a-a4dc4777bf31    M1           94108 
04d2de8b-646f-4433-8738-76103344e6b2    M2           94206
07d09852e9ca439cb0c573c8292e64f5    M2           94103

此时查询正常工作，但我还没有“COUNT（时间戳）”列，我正试图弄清楚如何在LinqToSql中表示这一点。此外，日期表示为DateDiff函数的日期边界，而不是实际日期时间值。有人可以查看我的L2S翻译，看看我是否遗漏了什么？另外，如何获取添加到此翻译的时间戳计数？

============ UPDATE ==================

根据John的指导，最终的Linq查询如下所示： -

from recwishlist in RecommendWishlists
join virdevice in VirtualDevices on recwishlist.VirtualDeviceId equals virdevice.Id 
join phydm in PhysicalDeviceModels on virdevice.PhysicalDeviceModelId equals phydm.Id 
group new {recwishlist, phydm} by new {
   recwishlist.AppId,
   phydm.Name, 
   Date =SqlDateTime.MinValue.Value.AddDays(
             SqlMethods.DateDiffDay(SqlDateTime.MinValue.Value,recwishlist.Timestamp))
   } into gApp
   select new {
 gApp.Key.AppId,
 gApp.Key.Name,  
 gApp.Key.Date,
 Downloads = (Int64?)gApp.Count()
}

Answer 1

看起来您需要引用“gApp.Key.Timestamp”而不是“app.Timestamp”，因为您从“gApp”中选择，而“app”不再处于上下文中。

修改

所以，你当前的问题正在计算中。这应该很简单：

select new {App = gApp.Key.AppId, Model = gApp.Key.Model, Date = gApp.Key.Date, Count = gApp.Count() }

将SQL转换为Linq To SQL

1 个答案: