What is wrong with my hotel design

[suomenfani]

Hi,

I am new to db's and I need to make a very simple model of a hotel. I prepared it, but i was told it wasnt good because the business model is mixed up with the database. However, I have no idea what that means and what is wrong with the tables. Here are the tables, can I you tell me why the design isnt good?

Thank you so much.



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CREATE TABLE Guest (

name varchar(20),
reservNum number,
CONSTRAINT Guest_PK primary key(reservNum)
);


CREATE TABLE RoomService(

item varchar(20),
price number NOT NULL,

CONSTRAINT RoomService_PK
primary key (item)
);


CREATE TABLE Room(

hotel varchar(20),
num number(3),
floor number(2),
type varchar(10),

CONSTRAINT Room_PK PRIMARY KEY (hotel, num),
CONSTRAINT Room_Type CHECK (type IN (‘single’ ,’double’, ‘apartment’))
);


CREATE TABLE Reserve(

hotel varchar(20),
reservNum number,
room number,
checkin date NOT NULL,
checkout date NOT NULL,
pricePerNight number NOT NULL,
Boolean booked;

CONSTRAINT Reserve_PK PRIMARY KEY (reservNum),

FOREIGN KEY (hotel,room) REFERENCES Room(hotel,num) ON DELETE CASCADE,
FOREIGN KEY (reservNum) REFERENCES Guest(reservNum) ON DELETE CASCADE
);


CREATE TABLE Consumes(

reservNum number,
itemUsed varchar(20)NOT NULL,
quantity number,

FOREIGN KEY (reservNum) REFERENCES Guest(reservNum) ON DELETE CASCADE,
FOREIGN KEY (itemUsed) REFERENCES RoomService(item) ON DELETE CASCADE);


CREATE TABLE Bill(

reservNum number,
roomServiceTotal number,
roomTotal number,
GrandTotal number,

FOREIGN KEY (reservNum) REFERENCES Guest(reservNum) ON DELETE CASCADE
);