在T-SQL中将日期时间转换为nvarchar（8）

Question

I'm trying to convert a datetime column to ISO format, as yyyymmdd . For example, I would like to be able to convert '13 dec 2018' to '20181213'.

According to Microsoft's T-SQL Docs , I should be able to do this using

convert(nvarchar(8), '13 dec 2018', 112)

however this doesn't work - I get the result '13 dec 2', which looks to be nothing more than the original string cut down to 8 characters.

I have also tried using

convert(datetime, '13 dec 2018', 112)

which gives me the result of 'Dec 13 2018 12:00AM' - again, nothing like what the function is supposed to produce.

What I am doing wrong? I could solve the problem easily enough using datepart() and concatenated strings, but I'd rather use the more elegant approach if possible.

Answer 1

Combine them:

convert(nvarchar(8), convert(datetime, '13 dec 2018'), 112)

I don't recommend using the format 112 for the first conversion, because it is misleading. SQL Server is very good at converting without a format. If you do use one the appropriate one is 106 .

Answer 2

I figured it out - because I was entering the date as a string, and not converting it to a datetime value first, it was treating my date as if it were a string. When I handle it this way:

convert(nvarchar(8), cast('13 dec 2018' as datetime), 112)

I get the expected result, '20181213'.

Answer 3

select convert(nvarchar(8), cast(GETDATE() as datetime), 112) as TodayDate

Answer 4

YYYYMMDD format can obtain by datetime to varchar format.

select convert(varchar(8),convert(datetime, '13 dec 2018'),112)

The above query provides the required result