Designing a Database
Unleashing the Power of
Relational Database Design
Understanding Databases
There are three basic kinds of databases
called (1) flat file, (2) relational, and (3)
object-oriented.
A flat file database keeps all of the
records in a single file, in which the data
elements are separated by a break
character such as a comma or a tab.
The terms comma-delimited or tabdelimited refer to data stored in this
manner.
Comma Delimited Data
What Is a Data Table?
Flat file databases typically contain
just one data table, which is a
database structure that organizes
the data into rows and columns.
Each row contains one record, and the
columns contain the data fields that
the record comprises.
Visualizing a Data Table
What Is a Relational Database?
A relational database is a data structure
that comprises multiple tables containing
primary key columns through which the
records in one table can relate (i.e., key) to
the data in another table.
A data table’s primary key is a column in
which every entry is unique.
A foreign key is a data field that relates
the record to the table in which that same
column occurs as a primary key.
Visualizing
Relational
Data
What Is an Object-Oriented
Database?
The third and final kind of database
is called object-oriented, in which
programmers writing code in objectoriented languages can create
complex data structures in which one
data type can build upon, or inherit,
properties from another.
In this course, we deal with relational
databases.
Database Design Principles
Each table should have a column
containing a unique row ID number
to serve as the table’s primary key.
A table should store data for a
single type of entity.
A table should avoid columns that
are allowed to contain null values. If
you must have empty values, use an
empty string.
Database Design Principles
(continued)
A table should not have repeating
values.
A field should have the same
meaning in each row of a table.
Multiple instances of an entity
should not be represented as
multiple columns.
Three-Tier
Web Application Model