The document provides an overview of database concepts including:
- A database contains files which contain records made up of fields that store data. Maintaining accurate data involves adding, changing, and deleting records while validating entries.
- There are advantages to the database approach over traditional file processing, including reduced data redundancy and easier shared access to data.
- A database management system (DBMS) allows users to create, access, and manage a database. Popular data models include relational, object-oriented, and multidimensional.
- The web provides access to vast amounts of database information.
2. 18-1-2019
Contents
Section Heading Page
Number
DATABASE
DATA, INFORMATION
DATABASE
The hierarchy of data Maintaining data
Adding records
Changing records
Deleting records
Validating data ALPHABETIC/NUMBERIC CHECK
RANGE CHECK
CONSISTENCY CHECK
COMPLETENESS CHECK
CHECK DIGIT
File processing versus
data base
The Database approach
File processing system
Data base
management system
Data Security
RELATIONAL, OBJECT-ORIENTED, AND
MULTIDIMENSIONAL DATABASE
WEB DATABASE
DATABASE ADMINISTRATION
Appendices A Discovering Computers
3. Fundamentals
Fourth edition
DATABASES, DATA, AND INFORMATION
A database is a collection of data organized in a manner that allows
access, retrieval, and use of that data. Data is a collection of
unprocessed items, which can include text, numbers, images, audio,
and video. Information is processed data; that is, it is organized,
meaningful, and useful. Computers process data in a database into
information. A database at a members-only discount warehouse, for
example, contains data about members, e.g., member data, purchase.
A computer at the warehouse processes new member data and then
sends receipt and ID card information to the printers. With database
software, often called a database management system (DBMS), users
create a computerized database; add, change, and delete data in the
database; sort and retrieve data from the database; and create forms
and reports from the data in the database. Database software includes
many powerful features.
Data Integrity
Most companies realize that data is one of their more valuable assets
— because data is used to generate information. Many business
transactions take less time when employees have instant access to
information. To ensure that data is accessible on demand, a company
must manage and protect its data just as it would any other resource.
Thus, it is vital that the data has integrity and is kept secure.
THE HIERARCHY OF DATA
Data is organized in layers. In the computer profession, data is
classified in a hierarchy. Each higher level of data consists of one or
more items from the lower level. For example, a member has an
4. address, and an address
consists of letters and
numbers. Depending on the
application and the user,
different terms describe the
various
levels of the hierarchy.
A database contains files, a file contains records, a record contains
fields, and a field is made up of one or more characters. The Discount
Warehouse database contains four files: Member, Membership Plans,
Member Purchases, and Products. The Member file contains records
about current members. The Membership Plans file contains records
identifying a type of membership and its annual fee. The Member
Purchases file contains records about members’ purchases at the
discount warehouse, and the Products file contains records about
items for sale. Each field in a record contains many characteristics,
one of which is the field size.
Fields
A field is a combination of one or more related characters or bytes
and is the smallest unit of data a user accesses. A field name uniquely
identifies each field. When searching for data in a database, you often
specify the field name. Field names for the data in the Membership
Plans file are Membership Code, Membership Name, and Annual Fee.
A database uses a variety of characteristics, such as field size and data
type, to define each field. The field size defines the maximum number
of characters a field can contain. For example, the Membership Code
field contains two characters. Valid entries include BB (Basic
Business), AB (Advantage Business), BP (Basic Personal), and AP
(Advantage Personal) .The Membership Code field has a field size of
2. The type of data in a field is an important consideration. The data
types for fields in the Membership Plans and Member files. The data
5. type specifies the kind of data a field can contain and how the field is
used. Common data types include: • Text (also called alphanumeric)
— letters, numbers, or special characters • Numeric — numbers only
• AutoNumber — unique number automatically assigned by the
DBMS to each added record • Currency — dollar and cent amounts or
numbers containing decimal values • Date — month, day, year, and
sometimes time information • Memo — lengthy text entries • Yes/No
— only the values Yes or No (or True or False) • Hyperlink — Web
address that links to a document or a Web page • Object —
photograph, audio, video, or a document created in other program.
MAINTAINING DATA
File maintenance refers to the procedures that keep data current. File
maintenance procedures include adding records to, changing records
in, and deleting records from a file.
Validating Data
Validation is the process of comparing data with a set of rules or
values to find out if the data is correct. Many programs perform a
validity check that analyses entered data to help ensure that it is
correct. For instance, when a membership services associate adds or
changes data in a member record, the DBMS tests the entered data.
With an annual membership fee, you would expect to see numbers
before and after a decimal point. For example, a valid annual
membership fee is 30.00. An entry of XR.WP clearly is not correct. If
the entered data fails a validity check, the computer should display an
error message that instructs the user to enter the data again. Validity
checks reduce data entry errors. Various types of validity checks
include alphabetic checks, numeric checks, range checks, consistency
checks, and completeness checks. Check digits also validate data
accuracy. The following paragraphs describe the purpose of these
validity checks. The several of these validity checks and shows valid
6. data that passes the check and invalid data that fails the check.
FILEPROCESSINGVERSUSDATABASES
Almost all application programs use the file processing approach, the
database approach, or a combination of both approaches to store and
manage data.
File Processing Systems
In the past, many organizations exclusively used file
processing systems to store and manage data. In a typical file
7. processing system, each department or area within an
organization has its own set of files. The records in one file
may not relate to the records in any other file. Companies
have used file processing systems for many years. A lot of
these systems, however, have two major weaknesses: they
have redundant data and they isolate data. • Data Redundancy
— Each department or area in a company has its own files in a
file processing system. Thus, the same fields are stored in
multiple files. If a file processing system is used at the
discount warehouse, for example, the Member file and the
Member Purchases file store the same members’ names and
addresses. Duplicating data in this manner wastes resources
such as storage space and people’s time. When new members
are added or member data is changed, file maintenance tasks
consume additional time because people must update multiple
files that contain the same data. Data redundancy also can
increase the chance of errors. If a member changes his or her
address, for example, the discount warehouse must update the
address wherever it appears. In this example, the Address field
is in the Member file and also in the Member Purchases file.
If the Address field is not changed in all the files where it is
stored, then discrepancies among the files exist. • Isolated
Data — Often it is difficult to access data stored in separate
files in different departments. Sharing data from multiple,
separate files is a complicated procedure and usually requires
the experience of a computer programmer.
The Database Approach
When a company uses the database approach, many programs and
users share the data in the database. A discount warehouse’s database
most likely contains data about members, membership plans, member
purchases, and products. As shown in Figure 9-9, various areas within
the discount warehouse share and interact with the data in this
database. The database does secure its data, however, so only
authorized users can access certain data items. While a user is
8. working with the database, the DBMS resides in the memory of the
compute
Databasemanagementsystem
A database management system (DBMS), or database program, is
software that allows you to create, access, and manage a database.
DBMSs are available for many sizes and types of computers .
Whether designed for a small or large computer, most DBMSs
perform common functions.
RELATIONAL,OBJECT-ORIENTED,ANDMULTIDIMENSIONAL
DATABASES
Every database and DBMS is
based on a specific data
model. A data model consists
of rules and standards that
define how the database
organizes data. A data model
defines how users view the
organization of the data. It does not define how the operating system
actually arranges the data on the disk. Three popular data models in
use today are relational, object-oriented, and multidimensional. A
database typically is based on one data model. Some databases,
however, combine features of the relational and object-oriented data
models. The following sections discuss relational, object-oriented,
and multidimensional databases.
Relational Databases:
Today, a relational database is a widely used type of database. A
relational database is a database that stores data in tables that consist
of rows and columns. Each row has a primary key and each column
has a unique name.
Object-Oriented Databases:
9. An object-oriented database (OODB) stores data in objects. An object
is an item that contains data, as well as the actions that read or process
the data. A Member object, for example, might contain data about a
member such as Member ID, First Name, Last Name, Address, and so
on. It also could contain instructions about how to print the member
record or the formula required to calculate a member’s balance due.
Multidimensional Databases :
A multidimensional database stores data in dimensions. Whereas a
relational database is a two-dimensional table, a multidimensional
database can store more than two dimensions of data. These multiple
dimensions allow users to access and analyze any view of the
database data.
10. WEB DATA BASE:
One of the more profound features of the Web is the vast amount of
information it provides. The Web offers information about jobs, travel
destinations, television programming, pictures, movies, videos, local
and national weather, sporting events, and legislative information.
You can shop for just about any product or service, buy or sell stocks,
search for a job, and make airline reservations. Much of this and other
information on the Web exists in databases. Some Web databases are
collaborative databases.