我有一个 Blazor Web 应用程序,它已经在该领域工作了几个月。我想将数据库查询扩展到类似的“检测”组。
它是从 .NET 5 开始编写的,而就在今天已更新到 .NET 6 试图使其正常工作。
我想知道如何获得按TimeStamp
(DateTime 属性)排序的结果。我有一个内存数据库的工作示例,但生产将在 SQL Server 中。我在 SQL 方面不是很好,但我在 Management Studio 中玩了一段时间,但没有运气。
正确地注释掉OrderByDescending()
组的事情,但结果的顺序不正确。似乎 EF 翻译过程完全删除了该行,它对生成的查询或结果集没有任何影响。
var results = context.Detections
//Line below makes no change ignored by SQL Server. Works when using in memory DB.
//.OrderByDescending(det => det.TimeStamp)
.GroupBy(det => new
{
Year = det.TimeStamp.Year,
Month = det.TimeStamp.Month,
Day = det.TimeStamp.Day,
Hour = det.TimeStamp.Hour,
})
.Select(grp => new
{
Count = grp.Count(),
Detection = grp.OrderByDescending(det => det.TimeStamp).First(),
})
//The following line will not translate
//.OrderByDescending(det => det.Detection.TimeStamp)
.ToList();
如果有任何问题:
- Visual Studio 2022 (4.8.04084)
- .Net 6.0
- SQL Server 2019 (15.0.2080.9)
- *所有与 EF 相关的 NuGet 包均已更新至 6.0
编辑澄清
上面的代码段产生以下 SQL 查询。
SELECT [t].[c], [t0].[Id], [t0].[TimeStamp]
FROM (
SELECT COUNT(*) AS [c], DATEPART(year, [d].[TimeStamp]) AS [c0], DATEPART(month, [d].[TimeStamp]) AS [c1], DATEPART(day, [d].[TimeStamp]) AS [c2], DATEPART(hour, [d].[TimeStamp]) AS [c3]
FROM [Detections] AS [d]
WHERE [d].[TimeStamp] > DATEADD(day, CAST(-16.0E0 AS int), GETUTCDATE())
GROUP BY DATEPART(year, [d].[TimeStamp]), DATEPART(month, [d].[TimeStamp]), DATEPART(day, [d].[TimeStamp]), DATEPART(hour, [d].[TimeStamp])
) AS [t]
OUTER APPLY (
SELECT TOP(1) [d0].[Id], [d0].[TimeStamp]
FROM [Detections] AS [d0]
WHERE ([d0].[TimeStamp] > DATEADD(day, CAST(-30.0E0 AS int), GETUTCDATE())) AND (((([t].[c0] = DATEPART(year, [d0].[TimeStamp])) AND ([t].[c1] = DATEPART(month, [d0].[TimeStamp]))) AND ([t].[c2] = DATEPART(day, [d0].[TimeStamp]))) AND ([t].[c3] = DATEPART(hour, [d0].[TimeStamp])))
ORDER BY [d0].[TimeStamp] DESC
) AS [t0]
它产生类似于以下的结果。注意不按时间排序。
1 628591 2021-11-02 14:34:06.0442966
10 628601 2021-11-12 05:43:27.7015291
150 628821 2021-11-12 21:59:27.6444236
20 628621 2021-11-12 06:17:13.7798282
50 628671 2021-11-12 15:17:23.8893856
如果我ORDER BY [t0].TimeStamp DESC
在 Management Studio 中的 SQL 查询末尾添加,我会得到我正在寻找的结果(见下文)。我只需要知道如何在 LINQ 中编写它。
150 628821 2021-11-12 21:59:27.6444236
50 628671 2021-11-12 15:17:23.8893856
20 628621 2021-11-12 06:17:13.7798282
10 628601 2021-11-12 05:43:27.7015291
1 628591 2021-11-02 14:34:06.0442966
.OrderByDescending(det => det.Detection.TimeStamp)
在最后添加ToList()
是我的第一个想法,但“无法翻译”。我需要对这些结果进行分页,所以我真的很想在 SQL 中进行排序。