CHAPTER 5: DATABASE SYSTEMS & BUSINESS INTELLIGENCE
•Data management and modeling are key aspects of organizing data and
information.
Data is one of the most valuable resources that a firm possesses. It is organized into a hierarchy
that builds from the smallest element to the largest. The smallest element is the bit, a binary digit.
A byte (a character such as a letter or numeric digit) is made up of eight bits. A group of
characters, such as a name or number, is called a field (an object). A collection of related fields is
a record; a collection of related records is called a file. The database, at the top of the hierarchy,
is an integrated collection of records and files. An entity is a generalized class of objects for which
data is collected, stored, and maintained. An attribute is a characteristic of an entity. Specific
values of attributes—called data items—can be found in the fields of the record describing an
entity.
A data key is a field within a record that is used to identify the record. A primary key uniquely
identifies a record, while a secondary key is a field in a record that does not uniquely identify the
record. Traditional file-oriented applications are often characterized by program-data
dependence, meaning that they have data organized in a manner that cannot be read by other
programs. To address problems of traditional file-based data management, the database
approach was developed. Benefits of this approach include reduced data redundancy, improved
data consistency and integrity, easier modification and updating, data and program
independence, standardization of data access, and more-efficient program development.
One of the tools that database designers use to show the relationships among data is a data
model. A data model is a map or diagram of entities and their relationships. Enterprise data
modeling involves analyzing the data and information needs of an entire organization. Entity-
relationship (ER) diagrams can be employed to show the relationships between entities in the
organization. The relational model places data in two-dimensional tables. Tables can be linked by
common data elements, which are used to access data when the database is queried. Each row
represents a record. Columns of the tables are called attributes, and allowable values for these
attributes are called the domain. Basic data manipulations include selecting, projecting, and
joining. The relational model is easier to control, more flexible, and more intuitive than the other
models because it organizes data in tables.
•A well-designed and well-managed database is an extremely valuable tool in
supporting decision making
A DBMS is a group of programs used as an interface between a database and its users and other
application programs. When an application program requests data from the database, it follows
a logical access path. The actual retrieval of the data follows a physical access path. Records can
be considered in the same way: A logical record is what the record contains; a physical record is
