Best Design for a booking system

Question

I am trying to create a booking database...but the design I keep coming up with makes me a bit uneasy. I don't really like it (because of massive joins involved in determining what time slots are available) but I don't see any other way to do this. So this is my design.
--This table stores incidences of booked time slots
TABLE:Booking_Incidence
BookingID
BookingStartDate (DateTime)
BookingEndDate (DateTime)
FK_UserID
--This Table stores the generally available booking times for each week.  Eg.  If users can book from 9:00am to 5:00pm monday to friday then there would be an entry with
slotstarttime = 9:00, slotendtime=17:00,sun=false,mon=true,tue=true, wed=true, thur=true, fri=true, sat=false
TABLE:General_Avail_Booking
SlotStartTime (Time)
SlotEndTime (Time)
Sun (boolean)
Mon (boolean)
Tue (boolean)
Wed (boolean)
Thur (boolean)
Fri (boolean)
Sat (boolean)
--This table stores any possible exceptions that might occur outside of the general booking times (eg a holiday).  bAvailable determines if the exception allows for a new booking, or cancels an existing one.
Table: Booking_Exceptions
SlotStartDate (DateTime)
SlotEndDate (DateTime)
bAvailable (boolean)
I use General_Avail_Booking and Booking_Exceptions to determine the possible times when users can actually book a time slot, and then store what time slots users book in Booking_Incidence.

Answer 1

You're thinking about the problem visually and so you have something that looks like a wall planner turned into SQL. Way too linear. A booked room is really an intersection between three dimensions - the room, the time it's booked for and the booking itself (who booked it, purpose, etc). If you track the bookings you can infer the times when the room is free.
The following code is very much an "it's almost Easter" spike and not guaranteed not to have its own problems.
SQL> CREATE TABLE booking
  2   (id number not null
  3     , booked_by varchar2(20) not null
  4     , booked_on date not null
  5     , CONSTRAINT book_pk PRIMARY KEY (id))
  6  /
Table created.
SQL> CREATE TABLE room
  2       (id number not null
  3        , location varchar2(10)
  4        , CONSTRAINT room_pk PRIMARY KEY (id))
  5  /
Table created.
SQL> CREATE TABLE slot
  2       (id number not null
  3        , slot_time varchar2(10)
  4        , CONSTRAINT slot_pk PRIMARY KEY (id))
  5  /
Table created.
SQL> CREATE TABLE booked_slot
  2   (room_id number not null
  3    , booked_date date not null
  4    , slot_id number not null
  5    , booking_id number not null
  6    , CONSTRAINT bslot_pk PRIMARY KEY (room_id, booked_date, slot_id)
  7    , CONSTRAINT bslot_book_fk FOREIGN KEY (booking_id)
  8       REFERENCES booking(id))
  9  /
Table created.
SQL> CREATE OR REPLACE TRIGGER bslot_bir BEFORE INSERT ON booked_slot
  2  FOR EACH ROW
  3  BEGIN
  4      :NEW.booked_date := trunc(:NEW.booked_date);
  5  END;
  6  /
Trigger created.
SQL>What I'm going to do here is have a little business rule that says you can't book a room for less than half an hour.
SQL> INSERT INTO slot VALUES (1000, '10:00')
  2  /
1 row created.
SQL> INSERT INTO slot VALUES (1030, '10:30')
  2  /
1 row created.
SQL> INSERT INTO slot VALUES (1100, '11:00')
  2  /
1 row created.
SQL> INSERT INTO slot VALUES (1130, '11:30')
  2  /
1 row created.
SQL> INSERT INTO slot VALUES (1200, '12:00')
  2  /
1 row created.
SQL> INSERT INTO slot VALUES (1230, '12:30')
  2  /
1 row created.
SQL> INSERT INTO slot VALUES (1300, '13:00')
  2  /
1 row created.
SQL> INSERT INTO slot VALUES (1330, '13:30')
  2  /
1 row created.
SQL> INSERT INTO room VALUES (1, '3/A')
  2  /
1 row created.
SQL> INSERT INTO room VALUES (2, '3/B')
  2  /
1 row created.
SQL> INSERT INTO room VALUES (3, 'Rm 8')
  2  /
1 row created.
SQL>Set done, let's book room 3/B for an hour and a half....
SQL> INSERT INTO booking VALUES (1, 'APC', sysdate)
2 /
1 row created.
SQL> INSERT INTO booked_slot VALUES (2, sysdate + 3, 1130, 1)
2 /
1 row created.
SQL> INSERT INTO booked_slot VALUES (2, sysdate + 3, 1200, 1)
2 /
1 row created.
SQL> INSERT INTO booked_slot VALUES (2, sysdate + 3, 1230, 1)
2 /
1 row created.
SQL>
But now the Easter Rabbit needs to book a room for two hours on Sunday. Which rooms are free?
SQL> SELECT room.location
  2  FROM   room
  3  WHERE  NOT EXISTS
  4         ( SELECT null
  5           FROM   booked_slot
  6           WHERE  room_id = room.id
  7           AND    booked_date = to_date('16-APR-2006')
  8           AND    slot_id BETWEEN 1000 AND 1200 )
  9  /
LOCATION
3/A
Rm 8
SQL>You'll notice the value of making the slot keys the same as the time they represent.
Of course, producing a map of availability is not that easy, but it should not that hard either.
Cheers, APC