Introduction - Database Processing: Fundamentals, Design, and Implementation - page 18

Figure 1-19
Databases Originating
from Existing Data

Spreadsheet
Spreadsheet
Spreadsheet
Spreadsheet

Database
Design

Text
files Text

files Text

files

Text
File

OR

Operational
Database
(ERP, CRM)

Database
Design

Database extraction

When creating a database from existing data, database developers must determine the
appropriate structure for the new database. A common issue is how the multiple files or tables
in the new database should be related. However, even the import of a single table can pose de-
sign questions. Figure 1-20 shows two different ways of importing a simple table of employees
and their departments. Should this data be stored as one table or two?
Decisions such as this are not arbitrary. Database professionals use a set of principles, col-
lectively called normalization , or normal forms , to guide and assess database designs. You
will learn those principles and their role in database design in Chapter 3.

Database Design for New Systems Development
A second way that databases are designed is for the development of new information systems.
As shown in Figure 1-21, requirements for a new system, such as desired data entry forms and

EmpNum EmpName DeptNum DeptName DeptNum DeptName

100 Jones 10 Accounting 10 Accounting

150 Lau 20 Marketing 20 Marketing

OR? 200 McCauley 10 Accounting

300 Griffin 10 Accounting

EmpNum EmpName DeptNum

(a) One-Table Design

100 Jones 10

150 Lau 20

200 McCauley 10

300 Griffin 10

Figure 1-20
Data Import: One or two
tables?

(b) Two-Table Design