Question

I try to create an application for the iPhone where you can set appointments. Everything is saved into a MySQL database and I currently get the data through JSON into my app. This is a workflow:

• User1 defines when he is working. E.g. 8am – 4pm.
• User2 wants to have an appointment with user1, e.g. 8am-9am.

The script should be able to do this:

• the appointment is within the user’s work hours; and
• it does not clash with an existing appointment, which can happen in three possible ways:
  • the clashing appointment starts during the new appointment; and/or
  • the clashing appointment ends during the new appointment; or
  • the clashing appointment starts before and ends after the new appointment.

These are the important tables:

// new row should be added here when the conditions above are met
create table ios_appointment (
   appointmentid int not null auto_increment,
   start timestamp,
   end timestamp,
   user_id_fk int
)

// a working hour has a n:1 relationshipt to ios_worker
create table ios_workinghours (
   workinghoursid int not null auto_increment,
   start timestamp,
   end timestamp,
   worker_id_fk int
)

// employee, has a 1:n relationship to ios_workinghours
create table ios_worker (
   workerid int not null auto_increment,
   prename varchar(255),
   lastname varchar(255),
   ...
)

The input for the select clause are two timestamps, start and end. These are defined by the user. So the script should check if user 2 is working at that specific time and if there are already appointments.

I currently have something like this, but that uses the user_id to link the tables:

SELECT EXISTS (
  SELECT *
  FROM   ios_appointments a JOIN ios_workhours h USING (user_id)
  WHERE  user_id = 1
     AND h.start <= '08:00:00' AND h.end >= '09:00:00'
     AND (
               a.start BETWEEN '08:00:00'  AND  '09:00:00'
           OR  a.end   BETWEEN '08:00:00'  AND  '09:00:00'
           OR (a.start < '08:00:00' AND a.end > '09:00:00')
         )
  LIMIT  1
)

Every help is appreciated. Thx.

Answer 1

You either need to have your app read in the data and determine if the time is available OR you need to create a view that has the available “time slots” (e.g. every 30 minutes).

Here’s how I would do it:

CREATE TABLE #timeslot
(
timeslot_id INT PRIMARY KEY IDENTITY(1,1),
timeslot_time DATETIME NOT NULL
)

DECLARE @startime DATETIME, @endtime DATETIME
SELECT @starttime = '12/25/2012 08:00:00.000', @endtime = '12/25/2012 15:00:00.000'

WHILE @starttime < @endtime BEGIN
   INSERT INTO #timeslot (timeslot_time)
    VALUES (@starttime)
    SET @starttime = DATEADD(mm,30,@starttime)
END

SELECT
   w.workerid,
   ts.timeslot_time
INTO
   ios_workertimeslot
FROM
   #timeslot ts
FULL OUTER JOIN
   ios_worker w
   ON  (1 = 1)


SELECT
   wts.workerid,
   wts.timeslot_time,
   ap.appointmentid,
   CASE WHEN ap.appointmentid IS NOT NULL THEN 0 ELSE 1 END AS AvailableSlot
FROM
   ios_workertimeslot wts
JOIN
   ios_workinghours wh
   ON  (wts.workerid = wh.workerid)
   AND (wts.timeslot_time >= wh.start)
   AND (wts.timeslot_time < wh.end)
LEFT JOIN
   ios_appointment ap
   ON  (wts.workerid = ap.workerid)
   AND (wts.timeslot_time >= ap.start)
   AND (wts.timeslot_time < ap.end)

This will leave you with a data set that indicates the available and non-available timeslots.

Hope this helps!