One to Many / Cruise ship site

Question

Hi, I am developing an e commerce site for a cruise ship company as part of a project for my college degree.
In my database I have some tables as follows:
create table cruisebooking (
cruise_id number,
cruise_dest varchar2(20),
cruise_date date,
cabin_number number,
cabin_avail integer,
FOREIGN KEY(cruise_id)
REFERENCES cruisedetails(cruise_id)
create table cruisedetails (
cruise_id number primary key,
cruise_name varchar2(20),
cruise_date date,
cruise_month varchar(15),
cruise_dest varchar2(20),
noofdays number,
cruise_price float
I want to have 10 cabins associated with each cruise for booking.
There is only one ship with 10 cabins so . .
cruise 1 will have 10 cabins
cruise 2 will have 10 cabins and so on . . .
How do I make it so that each cruise will have 10 cabins? So if cruise 1 is selected the user moves to the cabin reservation page and chooses a cabin (1-10) for that cruise!
I would like any help on this PLEASE !!! Thank you !

Answer 1

You need to have a separate entity CABIN. There are attributes for each CABIN eg (single/double/suite), location (port/starboard), class (first/steerage) etc. CRUISEBOOKING them becomes an intersection table between CABIN and CRUISEDETAILS.
Incidently cruise_dest and cruise_dest don't belong on CRUISEBOOKING - you've got them on CRUISEDETAILS. That is what we call normalisation.
You probably do what to have another entity PASSENGER which also intersects with CRUISEBOOKING. You can work out its attributes for yourself ;)
To answer your question:
How do I make it so that each cruise will have 10 cabins?The easiest way to do this is programmatically. When you create a new record for CRUISEDETAILS you create ten new CRUISEBOOKING records, with cabin availability = Y. (As I type this I start to have doubts about the name of this table and hence your entire data model but I don't really want to open that particular can of worms). Anyway, looking at this I think you might want to have these details stored in two tables (SHIP and CABINTYPE) even though you've only got one ship at the moment.
If you do go down that route you will need to use a stored procedure. If you want to hardcode the one ship/ten cabin model you could get away with a BEFORE INSERT trigger on CRUISEDETAILS. Note that this is implementation. I think you should flesh out your data model before you go think about such things.
You may be wondering why you have to do this programmatically. This is because of the nature of SQL and relational integrity. We can enforce the rule that every child record must have a parent but we cannot enforce the obverse rule, that every parent must have a child. (well actually there are workarounds but you really don't want to go there).
Cheers, APC