将本地DateTime与DateTimeOffset进行比较

Question

我有一个带有DateTime列的数据库，并希望将其与某些DateTimeOffset进行比较。DateTime列在（服务器）本地时间中。除了关于它的wtf'yness之外，我无能为力，我喜欢经常和强烈地做，所以我现在可以在这里跳过。

我希望能够从DateTime X在DateTimeOffset之前的表中选择所有行。我可以假设，如果现在是服务器上的DST，那么DateTime列也在DST中，反之亦然。这些时间将围绕"现在"进行本地化，日期（几乎）在过去的几个小时中总是存在。我将在下巴上进行DST更改，但是在DST或非DST中，解决方案不应总是错误的。

。

作为奖励要求，表格很大，因此在DateTime上执行任何操纵的问题都是不可能的。我想我想的是我正在寻找相当于

的

DECLARE @dto datetimeoffset(4) = '12-10-25 12:32:10 +06:00';
DECLARE @dt datetime = --this is where the magic happens?
SELECT * FROM MyTable WHERE datetimecol < @dt

有人可以帮助我实现魔术吗？

Answer 1

您需要一个SQL CLR函数来执行此操作。受这篇文章的启发，我写了以下内容：

using System;
using Microsoft.SqlServer.Server;
public class UserDefinedFunctions
{
    [SqlFunction(IsDeterministic = false)]
    public static DateTime? ConvertDateTimeOffsetToLocalDateTime(DateTimeOffset? dto)
    {
        if (!dto.HasValue)
            return null;
        return dto.Value.ToLocalTime().DateTime;
    }
}

您可以根据愿意自行编译，或者仅使用以下内容部署它，其中包含串行的二进制和SQL部署脚本：

EXEC sp_configure 'clr enabled', 1;
GO
RECONFIGURE
GO
CREATE ASSEMBLY [SqlClrDateTime]
FROM 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WITH PERMISSION_SET = SAFE
GO
CREATE FUNCTION dbo.ConvertDateTimeOffsetToLocalDateTime(@dto datetimeoffset)
RETURNS datetime2
AS EXTERNAL NAME SqlClrDateTime.UserDefinedFunctions.ConvertDateTimeOffsetToLocalDateTime
GO

这是您可以在方案中使用它的方法：

DECLARE @dto datetimeoffset(4) = '12-10-25 12:32:10 +06:00'
DECLARE @dt datetime = dbo.ConvertDateTimeOffsetToLocalDateTime(@dto) 
SELECT * FROM MyTable WHERE datetimecol < @dt