Question

I need to find whether a new schedule overlaps any existing schedules.

This is the “intervals” table:

     id  first              last    
     1   1900-01-01 09:00   1900-01-01 10:00
     2   1900-01-01 15:00   1900-01-01 18:00
     3   1900-01-01 18:01   1900-01-01 08:00

I am using a scalar function dbo.TimeOnly for extracting time part from the datetime fields.

My selection criteria as follows

First case

     declare @start datetime
     declare @end datetime

     set @start = dbo.TimeOnly('2011-may-11 08:01:00');
     set @end = dbo.TimeOnly('2011-may-11 15:30:00');

     select  * from intervals where 
     ( NOT ( dbo.TimeOnly(last) < @start OR  @end < dbo.TimeOnly(first) ) )

This will return 1st and 2nd records. I got this logic from Check whether the schedule overlaps each other?

Second case

    set @start = dbo.TimeOnly('2011-may-11 07:01:00');
    set @end = dbo.TimeOnly('2011-may-11 08:30:00');

How do I write a query that will return only the 3rd record for the criteria in the second case?

UPDATE

I will give more details for my problem

Different people are managing a particular event for a certain time duration in a day.

For Monday, the schedule format is like this

    Id  Start       End          User   Days    
     1  00:01 AM    08:00 AM     'A'    1
     2  08:01 AM    04:00 PM     'B'    1
     3  04:00 PM    00:00 AM     'C'    1

For Tuesday’s

     4  08:01 AM    04:00 PM     'B'    2
     5  07:00 PM    07:00 AM     'C'    2

For Wednesday’s

     6  08:01 AM    04:00 PM     'A'    4
     7  10:00 PM    08:00 AM     'B'    4

Here days are stored in the bit value format ie

Monday=1,Tuesday=2,Wednesday=4,Thursday=8,Friday=16,Saturday=32 and Sunday=64

When we creating a schedule for a particular day, it should not overlap between times.
I would like to get a SQL query for checking any schedules exists while creating a new schedule for a particular day.

For a particular event time (Say An even occured at 04:00 AM on Tuesday) I would like to find the correct schedule (Will be “5”) that falls between the Start and End time.

Answer 1

Change your SELECT to this:

select  * from intervals where 
(
( dbo.TimeOnly(last) > dbo.TimeOnly(first)
AND
NOT (dbo.TimeOnly(last) < @start OR  @end < dbo.TimeOnly(first)) )

OR

( dbo.TimeOnly(last) < dbo.TimeOnly(first)
AND
( @start >= dbo.TimeOnly(first) OR @end <= dbo.TimeOnly(last) OR (@start < dbo.TimeOnly(first) AND @end > dbo.TimeOnly(last)) ) )
)

I might’ve missed a parenthesis somewhere, but I hope not.

The concept here is a query with 2 main groupings combined with an OR. The first clause checks intervals where last > first and is mainly a copy of your existing query with the addition of the last > first condition, while the 2nd clause checks intervals where last < first.

In the case where last < first, there are 3 ways that an interval can overlap:

• start is after the interval’s first
• end is before the interval’s last
• start and end completely engulf the interval, i.e., start is before first and end is after last

Any one of these 3 conditions would mean the schedule to check is within an existing interval, so the 3 conditions are combined with ORs.