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SQL / TSQL - DATETIME - To The Nearest Half Hour, Hour, 2nd Hour, MORE:

Last Modified: 2011-10-03

I've searched quite a bit and found a few solutions but not anything solid that currently works.  What I'm trying to do is basically round the time part to the nearest 30 minute, hour, etc...as displayed below:

Rounding the same as numbers such as if rounding to the nearest 10th, 4.9 is 0, 5 is 10, 12.2 is 10, etc...Same concept with time.

ITEMS LOOKING FOR: (the date should not be considered at all, will be removed, no problem on this)
1) Round to the nearest Half Hour
2) Round to the nearest Hour
* 3) Round to the nearest 2nd Hour in a 24-Hour period
** 4) Round to the nearest 4th Hour in a 24-Hour period
*** 5) Round to the nearest 6th Hour in a 24-Hour period
**** 6) Round to the nearest 12th Hour in a 24-Hour period

* 2ND HOUR - 24-Hour period would be 12:00 AM, 2:00 AM, 4:00 AM, etc...all the way to 10:00 PM being the last 2-Hour period.

** 4TH HOUR - 24-Hour period would be 12:00 AM, 4:00 AM, 8:00 AM, etc...all the way to 8:00 PM being the last 4-Hour period.

*** 6TH HOUR - 24-Hour period would be 12:00 AM, 6:00 AM, 12:00 PM, and 6:00, all being the complete 6-Hour period.

**** 12TH HOUR - 24-Hour period would be 12:00 AM and 12:00 PM, both being the complete 12-Hour period.

Watch Question

this is how to diassemble the date time - assume date_col is a datetime column
datepart (arg, date_col) will return a part of a date according to arg
Datepart Abbreviations
to get the year use yy or yyyy
to get the month use mm or m
to get the day use dd or d
to get the hour use hh
to get the minute use mi or n
to get the second use ss or s

in order to assemble the date back, you just use the same function, and concat, for example
select   cast( char(years)+'.'+char(months)+'.'+char(days) etc... as datetime)
the format depends on the format of dates that you use
this format is always acceptable
also consider using the dateadd function


Hi momi,
Taking out the date part, vice versus, isn't a problem.  It's rounding to the nearest time interval (i.e.: Half Hour, Hour, 2nd Hour, 4th Hour, 6th Hour, or 12th Hour) in a 24-Hour period, without date aspects considered, time only.  I can actually get rounding to the nearest Hour fine, bit of trouble though when dealing with 30 minute, 2nd hour, etc...
i did not really understand the logic by which you do the rounding, so i'll assume that if x<5 then x is rounded to 0, otherwise it is rounded to 10
assuming m holds the minutes, and h hold the hours

round to 30m :
if m < 15 then
   set @m = 0
else if m >= 15 and m < 45
   set @m = 30
else if m >= 45
   set @m = 0
   set @h = @h + 1

something ilke that is ok ?
Top Expert 2008
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Top Expert 2008

If you don't need to remove the date part from the time, you can use this instead.
CREATE function [dbo].[RoundTime] (@Time datetime, @RoundTo float)
returns datetime
declare @RoundedTime smalldatetime
declare @Multiplier float
set @Multiplier= 24.0/@RoundTo
set @RoundedTime= ROUND(cast(@Time as float) * @Multiplier,0)/@Multiplier
return @RoundedTime

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Awesome, that was perfect!  Thanks e!

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