Question

T-SQL DateTime Question.

I have a set of time ranges. During those time ranges there could be a set of overlapping time ranges that I call ‘blocked’ out time. The blocked time wouldn’t span more than one day. What I want to do is split the time to exclude the blocked out time, basically giving me the time ranges that are not ‘blocked’. Its safe to assume that blocked times cant fall outside of the times ranges.

Example: I work 9am to 5pm with a 30 min lunch break at 1pm. I want the result of 2 rows: 9am to 1pm and 1.30pm to 5pm.

As mentioned, I have a set of time ranges so in the above example the working hours may differ on a daily basis and the number of breaks as well as their duration may differ.

I guess in terms of SQL the input parameters would look like this:

declare @timeranges table ( StartDateTime datetime, EndDateTime datetime )
declare @blockedtimes table ( StartDateTime datetime, EndDateTime datetime )

insert into @timeranges 
select '01 Jan 2009 09:00:00', '01 Jan 2009 17:00:00'
union select '02 Feb 2009 10:00:00', '02 Feb 2009 13:00:00'

insert into @blockedtimes 
select '01 Jan 2009 13:00:00', '01 Jan 2009 13:30:00'
union select '02 Feb 2009 10:30:00', '02 Feb 2009 11:00:00'
union select '02 Feb 2009 12:00:00', '02 Feb 2009 12:30:00'

The result set would look like this.

Start                   End
---------------------   ---------------------
'01 Jan 2009 09:00:00' '01 Jan 2009 13:00:00'
'01 Jan 2009 13:30:00' '01 Jan 2009 17:00:00'
'02 Feb 2009 10:00:00' '02 Feb 2009 10:30:00'
'02 Feb 2009 11:00:00' '02 Feb 2009 12:00:00'
'02 Feb 2009 12:30:00' '02 Feb 2009 13:00:00'

I could do this with a cursor or while loop but if someone could suggest how to do this without iteration that would be great – thanks.

Answer 1

I thought I’d share the solution I finally settled on:

Slight adjustment to the temp table in that I’ve added a StartDate field to both @timeranges and @blockedtimes

declare @timeranges table ( StartDate datetime, StartDateTime datetime, EndDateTime datetime ) 
declare @blockedtimes table ( StartDate datetime, StartDateTime datetime, EndDateTime datetime )

Anyways seems simpler than some of the other answer posted – cheers for everyones help 🙂

select 
    *
from
(
    -- first SELECT get start boundry
    select t.StartDateTime s, b.StartDateTime e
    from @timeranges t, @blockedtimes b
    where 
        -- same day and blocks overlaps timerange
        t.StartDate = b.StartDate and (t.StartDateTime <= b.EndDateTime and b.StartDateTime <= t.EndDateTime)
    and
        -- the following is the important bit for this SELECT   
        not exists (select 1 from @blockedtimes b2 where b2.StartDate = b.StartDate and b2.StartDateTime < b.StartDateTime)
union
    -- second SELECT get spikes ie middle
    select b1.EndDateTime s, b2.StartDateTime e
    from @timeranges t, @blockedtimes b1, @blockedtimes b2
    where 
        -- same day and blocks overlaps timerange
        t.StartDate = b1.StartDate and (t.StartDateTime <= b1.EndDateTime and b1.StartDateTime <= t.EndDateTime) 
    and 
        -- same day and blocks overlaps timerange
        t.StartDate = b2.StartDate and (t.StartDateTime <= b2.EndDateTime and b2.StartDateTime <= t.EndDateTime) 
    and 
        -- the following is the important bit for this SELECT
        b1.EndDateTime < b2.StartDateTime
union
    -- third SELECT get end boundry
    select b.EndDateTime s, t.EndDateTime e
    from @timeranges t, @blockedtimes b
    where 
        -- same day and blocks overlaps timerange
        t.StartDate = b.StartDate and (t.StartDateTime <= b.EndDateTime and b.StartDateTime <= t.EndDateTime)
    and 
        -- the following is the important bit for this SELECT
        not exists (select 1 from @blockedtimes b2 where b2.StartDate = b.StartDate and b2.StartDateTime > b.StartDateTime)
) t1