Truncate a Datetime at different lengths without DATETRUNC

I want to truncate a datetime(7) at different lengths - determined by parts - in SQL Server 2019 (DATETRUNC starts on 2022 *). Kind of "year-month", "year-month-day", ... up to seconds.

• https://learn.microsoft.com/en-us/sql/t-sql/functions/datetrunc-transact-sql?view=sql-server-ver15

In case below I truncate up to minute (leaving seconds a precision):

SELECT
    FORMAT(DATEPART(year,my_col), '0000')
    + '-' + FORMAT(DATEPART(month,my_col), '00')
    + '-' + FORMAT(DATEPART(day,my_col), '00')
    + ' ' + FORMAT(DATEPART(hour,my_col), '00')
    + ':' + FORMAT(DATEPART(minute,my_col), '00') AS my_col  
FROM my_schema.my_table 

I get "2025-06-10 19:43" - which is OK.

Any shorter code that would do the work of DATETRUNC? And that (at best) would return a type of date and not string?

If your parts is a column with a format()-compatible string, you can directly use it to go to then back from string (convert for the "from" part):

select *, convert(datetime, format(my_col, parts), 120) truncated
from my_table;

(see it in a fiddle to test on)

Of course this requires that you have total control over parts, so that its format is not broken by user input!

If this is not the case, you'll rely on a mapping from each of your parts value to the corresponding format.