Question

I have a DateTime column. I want to extract all records, lets say, from 8:30 to 16:15 within a certain date range. My problem is that I need to compare hour and minute as a single time value. I can test the DATEPART for Greater or Less than some hours value, but if I then do that for minutes my query will fail if the later-in-the-day time has a smaller minutes value.

I have looked at INTERVAL, BETWEEN, DATEPART, DATEDIFF etc, but don’t see quite how to to this without a “TimeOfDay” value that I can use across records of different dates.

I have tried subtracting the year, month and day parts of the date so that I can compare just the time of day, but when attmpting to subract, say, the year part of a date I get an overlfow error:

This part works:

select - cast( DATEPART(YEAR, CallTime) as integer) from history

This fails:

select DATEADD(YEAR, - cast( DATEPART(YEAR, CallTime) as integer), CallTime) 
from history where calltime is not null

I have also tried casting the hours and minutes parts to chars, concatenating them and comparing to my target range, but this also fails.

I believe newer versions of SQL server may have a function to deal with this situation, but that’s not available to me.

I hope and imagine there is a simple, obvious solution to this, but it’s eluding me.

Answer 1

Try creating a “MinuteOfDay” function that calculates how many minutes have passed in the day based on a datetime.

CREATE FUNCTION dbo.[MinuteOfDay] 
(
    @dt datetime
)
RETURNS int
AS
BEGIN
    RETURN (datepart(hh,@dt)*60) + datepart(mi,@dt) 
END

then use the result of that function to filter.

select * 
from MyTable t 
where dbo.MinuteOfDay(t.SomeDateTimeColumn) between dbo.MinuteOfDay('1900-1-1 08:30:00') and dbo.MinuteOfDay('1900-1-1 16:15:00')