PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

210 Chapter 8 Designing Your Web Database
CUSTOMERS
CustomerID
Name
Address
City
1
Julie Smith
25 Oak Street
Airport West
2
Alan Wong
1/47 Haines Avenue
Box Hill
3
Michelle Arthur
357 North Road
Yarraville
ORDERS
OrderID
CustomerID
Amount
Date
1
3
27.50
02-Apr--2007
2
1
12.99
15-Apr-2007
3
2
74.00
19-Apr-2007
4
3
6.99
01-May-2007
Figure 8.2
Each order in the Orders table refers to a customer from the
Customers table.
The relational database term for this relationship is foreign key. CustomerID is the primary
key in Customers, but when it appears in another table, such as Orders, it is referred to
as a foreign key.
You might wonder why we chose to have two separate tables.Why not just store
Julie’s address in the Orders table? We explore this issue in more detail in the next
section.
Schemas
The complete set of table designs for a database is called the database schema. It is akin to
a blueprint for the database. A schema should show the tables along with their columns,
and the primary key of each table and any foreign keys. A schema does not include any
data, but you might want to show sample data with your schema to explain what it is
for.The schema can be shown in informal diagrams as we have done, in entity relationship
diagrams (which are not covered in this book), or in a text form, such as
Customers(CustomerID, Name, Address, City)
Orders(OrderID, CustomerID, Amount, Date)
Underlined terms in the schema are primary keys in the relation in which they are
underlined. Italic terms are foreign keys in the relation in which they appear italic.