Best approach to remove time part of datetime in SQL Server

Question

Which method provides the best performance when removing the time portion from a datetime field in SQL Server?

a) select DATEADD(dd, DATEDIFF(dd, 0, getdate(         


        

Answer 1

Here I made a function to remove some parts of a datetime for SQL Server. Usage:

• First param is the datetime to be stripped off.
• Second param is a char:
  • s: rounds to seconds; removes milliseconds
  • m: rounds to minutes; removes seconds and milliseconds
  • h: rounds to hours; removes minutes, seconds and milliseconds.
  • d: rounds to days; removes hours, minutes, seconds and milliseconds.
• Returns the new datetime

create function dbo.uf_RoundDateTime(@dt as datetime, @part as char) returns datetime as begin if CHARINDEX( @part, 'smhd',0) = 0 return @dt; return cast( Case @part when 's' then convert(varchar(19), @dt, 126) when 'm' then convert(varchar(17), @dt, 126) + '00' when 'h' then convert(varchar(14), @dt, 126) + '00:00' when 'd' then convert(varchar(14), @dt, 112) end as datetime ) end