将格式为20200321的bigint值转换为格式为'2020-03-21 00:00:00'的日期时间

Question

如何将id2 = mongoose.Types.ObjectId(req.user._id); （即bigint的{​​{1}}值20200321转换为date(2020-03-21格式21st March, 2020)，以便我们可以与其他表映射

Answer 1

您可以像这样简单地投射它：

select cast('20200321' as datetime2)

SQL Here

Answer 2

首先将bigint投射到varchar，然后投射到datetime。

declare @a as bigint = 20200321;
select CAST(CAST(@A AS varchar) as datetime)