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SQL Server round date to last quarter of an hour

How can I round a date down to the last quarter of an hour in SQL for SQL Server?

i.e. 01/01/2001 10:09:54 becomes 01/01/2001 10:00:00 and 01/01/2001 10:46:32becomes 01/01/2001 10:45:00

adathelad

Hi,

Not necessarily the most elegant but it works...

DECLARE @OriginalDate DATETIME
SET @OriginalDate = GETDATE()
DECLARE @Date DATETIME
SET @Date = CONVERT(VARCHAR(10), @OriginalDate, 120)
 
SELECT 
	CASE 
		WHEN DATEPART(mi, @OriginalDate) >=0 AND DATEPART(mi, @OriginalDate) <15 THEN DATEADD(HH, DATEPART(HH, @OriginalDate), @Date)
		WHEN DATEPART(mi, @OriginalDate) >=15 AND DATEPART(mi, @OriginalDate) <30 THEN DATEADD(mi, (DATEPART(HH, @OriginalDate) * 60) + 15, @Date)
		WHEN DATEPART(mi, @OriginalDate) >=30 AND DATEPART(mi, @OriginalDate) <45 THEN DATEADD(mi, (DATEPART(HH, @OriginalDate) * 60) + 30, @Date)
		WHEN DATEPART(mi, @OriginalDate) >=45 THEN DATEADD(mi, (DATEPART(HH, @OriginalDate) * 60) + 45, @Date)
	END

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adathelad

Wrapped up as a function, simplifies use to:

SELECT dbo.fnRoundToPreviousQuarterHour('2001-01-01 10:09:54')

CREATE FUNCTION dbo.fnRoundToPreviousQuarterHour(@Date DATETIME)
	RETURNS DATETIME
AS
BEGIN
DECLARE @RoundedDate DATETIME
SET @RoundedDate = CONVERT(VARCHAR(10), @Date, 120)
 
SELECT @RoundedDate = 
	CASE 
		WHEN DATEPART(mi, @Date) >=0 AND DATEPART(mi, @Date) <15 THEN DATEADD(HH, DATEPART(HH, @Date), @RoundedDate)
		WHEN DATEPART(mi, @Date) >=15 AND DATEPART(mi, @Date) <30 THEN DATEADD(mi, (DATEPART(HH, @Date) * 60) + 15, @RoundedDate)
		WHEN DATEPART(mi, @Date) >=30 AND DATEPART(mi, @Date) <45 THEN DATEADD(mi, (DATEPART(HH, @Date) * 60) + 30, @RoundedDate)
		WHEN DATEPART(mi, @Date) >=45 THEN DATEADD(mi, (DATEPART(HH, @Date) * 60) + 45, @RoundedDate)
	END
 
RETURN @RoundedDate
END

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ASKER CERTIFIED SOLUTION

Binuth

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adathelad

I like Binuth's - a lot more concise :)

Does need a small tweak as if you have milliseconds in the original time, those make it through to the result, but if you can sort that out then go for that

MooksUK

ASKER

Thank to both for your efforts. Neat solution Binuth.

grberk

just use smalldatetime if you only need precision to the quarter hour

declare @dt as smalldatetime
set @dt = getdate()
select dateadd(ss,-datepart(ss,@dt),dateadd(mi,-(datepart(mi,@dt)%15),@dt))