将 nvarchar 转换为日期时间 [英] Cast/Convert nvarchar to datetime

问题描述

我有桌子:

id   timestamp
1    31.10.2020 16:32:11
2    09.09.2020 09:15:49
3    22.04.2020 02:48:15

表中有大量这些数据.列时间戳是数据类型nvarchar".而且我需要按日期对数据进行排序或在 WHERE 子句中使用按日期进行约束，因此我需要将时间戳"转换为时间戳".到日期时间.但我不能.我试过转换和转换，但还是失败了.

Table have huge amount these data. Column timestamp is data type "nvarchar". And i need to sort datas by date or use in clauses WHERE for constraint by date, so i need to convert "timestamp" to datetime. But I can't. I tried convert and cast but still failed.

有什么建议吗?

谢谢.

推荐答案

修复您的设计，并将列更改为日期和时间数据类型.考虑到您的数据精确到 1 秒，datetime2(0) 在这里似乎很合适.首先，我们需要更改格式"nvarchar 值转换为 ISO 格式.我们将使用 ISO8601 格式 (yyyy-mm-ddThh:mi:ss.mmm)，因为它是明确的:

Fix your design, and change the column to a date and time data type. Considering your data is accurate to 1 second, a datetime2(0) seems appropriate here. First we need to change the "format" of the nvarchar value to an ISO format. We're going to use the ISO8601 format (yyyy-mm-ddThh:mi:ss.mmm) as it's unambiguous:

UPDATE dbo.YourTable
SET [timestamp] = CONVERT(nvarchar(20),TRY_CONVERT(datetime2(0), [timestamp], 4), 126);

现在您可以ALTER表格并将数据类型更改为datetime2(0):

Now you can ALTER the table and change the data type to a datetime2(0):

ALTER TABLE dbo.YourTable ALTER COLUMN [timestamp] datetime2(0) NULL;

我还建议为您的列使用与 timestamp 不同的名称.timestamp 是 rowversion 的弃用同义词，因此它的使用会使它变得相当混乱；特别是 rowversion 不是日期和时间值，而是 binary 值，并且不能转换为日期和时间数据类型.

I also recommend using a different name than timestamp for your column. timestamp is a deprecated synonym for rowversion, so it's use can make it quite confusing; especially as rowversion is not a date and time value but a binary value and cannot be converted to a date and time data type.

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