Appointment booking available time - sql-server

Question

I would like to get the list of available time for the given date and duration form the tblAppointments table
tblAppointments
id int
BookingDate datetime
BookedStartTime datetime
BookedEndTime datetime
Sample Data in the table
id BookingDate BookedStartTime BookedEndTime
1 2014-02-03 00:00:00 2014-02-03 08:30:00 2014-02-03 09:00:00
2 2014-02-03 00:00:00 2014-02-03 09:00:00 2014-02-03 10:30:00
3 2014-02-03 00:00:00 2014-02-03 12:00:00 2014-02-03 14:30:00
4 2014-02-03 00:00:00 2014-02-03 15:00:00 2014-02-03 16:30:00
If I give a input parameters as
BookingDate : 2014-02-03
DurationCode : 1 (eg 30 minutes)
I would like to get the result as below
2014-02-03 08:00:00 2014-02-03 08:30:00
2014-02-03 10:30:00 2014-02-03 11:00:00
2014-02-03 11:00:00 2014-02-03 11:30:00
2014-02-03 11:30:00 2014-02-03 12:00:00
2014-02-03 14:30:00 2014-02-03 15:00:00
2014-02-03 16:30:00 2014-02-03 17:00:00
If the input parameters are
BookingDate : 2014-02-03
DurationCode : 2 (eg 15 minutes)
The results should be like given below
2014-02-03 08:00:00 2014-02-03 08:15:00
2014-02-03 08:15:00 2014-02-03 08:30:00
2014-02-03 10:30:00 2014-02-03 10:45:00
2014-02-03 10:45:00 2014-02-03 11:00:00
2014-02-03 11:00:00 2014-02-03 11:15:00
2014-02-03 11:15:00 2014-02-03 11:30:00
2014-02-03 11:30:00 2014-02-03 11:45:00
2014-02-03 11:45:00 2014-02-03 12:00:00
2014-02-03 14:30:00 2014-02-03 14:45:00
2014-02-03 14:45:00 2014-02-03 15:00:00
2014-02-03 16:30:00 2014-02-03 16:45:00
2014-02-03 16:45:00 2014-02-03 17:00:00
The start and end appointment are 08:00 and 18:00
I have written a stored procedure for the same, which seems to be working, but I would like to know if there is any simple way to do the same.
The Stored Procedure is
ALTER Procedure [dbo].[FindAvailableTime] (
#BookingDate datetime,
#DurationCode int
)
as
Declare #Duration datetime
Declare #DurationMinutes int
Declare #DurationHours int
select #Duration = Duration from DurationCode where DurationCodeID = #DurationCode
Set #DurationMinutes = datepart(minute,#Duration)
Set #DurationHours = datepart(hour,#Duration)
if (#DurationHours > 0)
Begin
Set #DurationMinutes = #DurationMinutes + (#DurationHours * 60)
End
Declare #StartTimeHR int
Declare #StartTimeMN int
Declare #EndTimeHR int
Declare #EndTimeMN int
Declare #CurrentDateTimeStart datetime
Declare #CurrentDateTimeStartString varchar(100)
Declare #CurrentDateTimeEnd datetime
Declare #CurrentDateTimeEndString varchar(100)
Declare #CurrentDateTimeEndWork datetime
Declare #CurrentDateTimeEndStringWork varchar(100)
Declare #CurrentYear int
Declare #CurrentMonth int
Declare #CurrentDay int
Set #CurrentYear = datepart(year,#BookingDate)
Set #CurrentMonth = datepart(month,#BookingDate)
Set #CurrentDay = datepart(day,#BookingDate)
Set #StartTimeHR = 8
Set #StartTimeMN = 0
Set #EndTimeHR = 18
Set #EndTimeMN = 1
Set #CurrentDateTimeStartString = convert(varchar(10),#CurrentYear) + '-' + convert(varchar(10),#CurrentMonth) + '-' + convert(varchar(10),#CurrentDay) + ' ' + convert(varchar(10),#StartTimeHR) + ':' + convert(varchar(10),#StartTimeMN) + ':' + '0'
Set #CurrentDateTimeEndString = convert(varchar(10),#CurrentYear) + '-' + convert(varchar(10),#CurrentMonth) + '-' + convert(varchar(10),#CurrentDay) + ' ' + convert(varchar(10),#EndTimeHR) + ':' + convert(varchar(10),#EndTimeMN) + ':' + '0'
set #CurrentDateTimeStart = convert(datetime, #CurrentDateTimeStartString)
set #CurrentDateTimeEnd = convert(datetime, #CurrentDateTimeEndString)
Declare #CurrentDateTimeEndTemp datetime
set #CurrentDateTimeEndTemp = dateadd(mi,#DurationMinutes,#CurrentDateTimeStart)
Declare #AppointmentStartTime datetime
Declare #AppointmentEndTime datetime
Declare #StartDate datetime
Declare #EndDate datetime
Declare #EndDateTemp datetime
Declare #StartDatePlusOne datetime
Declare #EndDateMinusOne datetime
set #StartDate = #CurrentDateTimeStart
set #EndDate = #CurrentDateTimeEnd
set #EndDateTemp = dateadd(mi,#DurationMinutes,#StartDate)
Set #StartDatePlusOne = dateadd(mi,1,#StartDate)
Set #EndDateMinusOne = DateAdd(mi,-1,#EndDateTemp)
Create Table #Appointment_AvailableTime (StartTime datetime, EndTime datetime)
if Exists (select * from tblAppointments where BookingDate = #BookingDate)
Begin
while (#EndDateTemp < #EndDate)
Begin
if not exists (Select * from tblAppointments where #StartDatePlusOne between BookedStartTime and BookedEndTime or #EndDateMinusOne between BookedStartTime and BookedEndTime)
begin
if not exists (Select * from tblAppointments where BookedStartTime Between #StartDatePlusOne and #EndDateMinusOne or BookedEndTime between #StartDatePlusOne and #EndDateMinusOne)
Begin
insert into #Appointment_AvailableTime values(#StartDate, #EndDateTemp)
set #StartDate = dateadd(mi,#DurationMinutes,#StartDate)
End
Else
Begin
Select #StartDate = max(BookedEndTime) from tblAppointments where BookedStartTime Between #StartDatePlusOne and #EndDateMinusOne or BookedEndTime between #StartDatePlusOne and #EndDateMinusOne
End
set #EndDateTemp = dateadd(mi,#DurationMinutes,#StartDate)
Set #StartDatePlusOne = dateadd(mi,1,#StartDate)
Set #EndDateMinusOne = DateAdd(mi,-1,#EndDateTemp)
End
Else
Begin
Select #StartDate = max(BookedEndTime) from tblAppointments where #StartDatePlusOne between BookedStartTime and BookedEndTime or #EndDateMinusOne between BookedStartTime and BookedEndTime
set #EndDateTemp = dateadd(mi,#DurationMinutes,#StartDate)
Set #StartDatePlusOne = dateadd(mi,1,#StartDate)
Set #EndDateMinusOne = DateAdd(mi,-1,#EndDateTemp)
End
End
End
Else
Begin
Set #CurrentDateTimeEndWork = dateadd(mi,#DurationMinutes,#CurrentDateTimeStart)
while (#CurrentDateTimeStart < #CurrentDateTimeEnd and #CurrentDateTimeEndWork < #CurrentDateTimeEnd)
Begin
insert into #Appointment_AvailableTime values(#CurrentDateTimeStart, #CurrentDateTimeEndWork)
set #CurrentDateTimeStart = dateadd(mi,#DurationMinutes,#CurrentDateTimeStart)
Set #CurrentDateTimeEndWork = dateadd(mi,#DurationMinutes,#CurrentDateTimeStart)
End
End
select StartTime, EndTime from #Appointment_AvailableTime
Thanks

Answer 1

Maintain a table that holds all valid appointment times. Putting all possible 1h, 30m, 15m slots during an 10 hour period is still tiny (70 rows). This makes adding more complex rules, like "no 1 hour appointments after 4pm" really easy. Adding a day-of-the-week column to the lookup table will let you trivially add things like "extended hours on wednesdays" or "half day saturdays".
CREATE TABLE tblAppointmentSlots (
DurationID int,
SlotStartTime datetime CHECK (CAST(SlotStartTime AS int) = 0),
SlotEndTime datetime CHECK (CAST(SlotEndTime AS int) = 0)
)
GO
INSERT tblAppointmentSlots VALUES
(1, '08:00', '08:30'),
(1, '08:30', '09:00'),
etc..
GO
ALTER Procedure [dbo].[FindAvailableTime] (
#BookingDate datetime,
#DurationCode int
)
AS
SELECT
#BookingDate + SlotStartTime,
#BookingDate + SlotEndTime
FROM tblAppointmentSlots
WHERE DurationID = #DurationCode
AND NOT EXISTS (
SELECT 1
FROM tblAppointments
WHERE #BookingDate + SlotStartTime < BookedEndTime
AND #BookingDate + SlotEndTime > BookedStartTime
)