Databases Reference
In-Depth Information
data involved. Also, just because the price of storage has dropped, installing
additional storage when you run out of space can be time consuming and usu-
ally means down time for the database, which typically is very expensive.
The third reason is not visible from the partial E-R diagram in Figure 4-3.
However, when you look at the full E-R diagram in Figure 4-5, the reason
Figure 4-5
OFFICE
*
Office Number
Telephone
Size
Works in
SALESPERSON
CUSTOMER
Salesperson
Number
Salesperson
Name
Commission
Percentage
Year of Hire
Customer
Number
Customer
Name
HQ City
*
*
Sells to
Sells
Quantity
Works for
CUSTOMER
EMPLOYEE
PRODUCT
Product
Number
Product
Name
Unit Price
*
*
Employee
Number
Employee
Name
Title
Full E-R diagram.
