Chapter 10 : Database Management
Assignment from Tri Djoko Wahjono, Ir., M.Sc.
1.
What Is a Database, and How Does a Database
Interact with Data and Information?
A database is a collection of data organized in a manner
that allows access, retrieval, and use of that data.
Database software, often called a database
management system (DBMS), allows users to create a computerized
database; add, modify, and delete the data; sort and retrieve the data; and
create forms and reports from the data.
Data is a collection of unprocessed items, which can include text,
numbers, images, audio, and video.
Computers process data into information. Information is
processed data; that is, it is organized, meaningful, and useful. In addition
to documents, information can be in the form of audio, images, and video.
2.
What Is Data Integrity, and What Are the
Qualities of Valuable Information?
Because data is used to generate information, many organizations
realize that data is one of their more valuable assets.
Data integrity identifies the quality of data.
Data integrity is important because computers and people use information to
make decisions and take actions. For a computer to produce correct information,
the data that is entered in a database must have integrity. For information to
be valuable, it should be accurate, verifiable, timely, organized, accessible,
useful, and cost-effective.
Accurate information is error free.
Verifiable information can be proven as correct or
incorrect.
Timely information has an age suited to its use.
Organized information is arranged to suit the needs and
requirements of the decision maker. Accessible information is available
when the decision maker needs it.
Useful information has meaning to the person who
receives it.
Cost-effective information should give more value than it
costs to produce.
3.
What Is
Meant by Character, Field, Record, and File?
Data is classified in a hierarchy, with each level of
data consisting of one or more items from the lower level.
A bit is the smallest unit
of data a computer can process.
Eight bits grouped
together in a unit form a byte, and each byte represents a single character, which can be a
number, letter, space, punctuation mark, or other symbol.
A field is a combination of one or more related
characters or bytes and is the smallest unit of data a user accesses.
A record is a group of related fi elds.
A data file is a collection of related
records stored on a storage medium such as a hard disk or optical disc.
4.
What Are
File Maintenance Techniques and Validation Techniques?
File maintenance refers to the procedures that
keep data current. File maintenance procedures include adding records when new
data is obtained, modifying records to correct inaccurate data or to update old
data with new data, and deleting records when they no longer are needed.
Validation is the process of comparing data with a set
of rules or values to fi nd out if the data is correct. Many programs perform a
validity check that analyzes data, either as you enter it or after you
enter it, to help ensure that it is correct. Types of validity checks include
an alphabetic check, a numeric check, a range check, a consistency
check, a completeness check, and a check digit.
5.
How Is a
File Processing Approach Different from the Database Approach?
In a file processing system, each department or area within
an organization has its own set of data fi les. The records in one fi le may
not relate to the records in any other fi le. Two major weaknesses of fi le
processing systems are redundant data (duplicated data) and isolated data.
With a database approach, many programs and users share the
data in a database. The database approach reduces data redundancy, improves
data integrity, shares data, permits easier access, and reduces development
time.
A database, however, can be more complex than a file processing
system, requiring special training and more computer memory, storage, and
processing power than
file processing systems. Data in a database also can be more
vulnerable than data in fi le processing systems.
6.
What
Functions Are Common to Most Database Management Systems?
Database management systems (DBMSs) are available for many sizes
and types of computers. Whether designed for a small or large computer, most
DBMSs perform common functions.
A data dictionary, sometimes called a repository, contains
data about each fi le in the database and each field in those fi les. A DBMS
offers several methods to retrieve and maintain data in the database, such as query
languages, query by example, forms, and report generators.
A query language consists of simple, English-like
statements that allow users to specify the data to display, print, or store.
Query by example (QBE)
has a graphical user interface that assists users with retrieving data. A form,
sometimes called a data entry form, is a window on the screen that
provides areas for entering or modifying data in a database.
A report generator, also called a report writer,
allows users to design a report on the screen, retrieve data into the report
design, and then display or print the report. To supply security, most DBMSs
can identify different levels of access privileges that defi ne the
actions aspecific user or group of users can perform for each field in a
database. If a database is damaged or destroyed, a DBMS provides techniques to
return the database to a usable form.
A backup is a copy of the database.
A log is a listing of activities that modify the contents
of the database.
A recovery utility uses the logs and/or backups to restore
the database using rollforward or rollback techniques. In a rollforward,
also called forward recovery, the DBMS uses the log to reenter changes made
to the database since the last save or backup. In a rollback, also
called backward recovery, the DBMS uses the log to undo any changes made
to the database during a certain period. Continuous backup is a backup
plan in which all data is backed up whenever a change is made.
7.
What Are
Characteristics of Relational, Object-Oriented, and Multidimensional Databases?
A data model consists of rules and standards that defi ne
how the database organizes data. Three popular data models are relational,
object-oriented, and multidimensional.
A relational database stores data in tables that consist of
rows and columns. A relational database developer refers to a fi le as a relation,
a record as a tuple, and a field as an attribute. A relational
database user refers to a file as a table, a record as a row, and
a fi eld as a column.
A relationship is a link within the data in a relational
database.
Structured Query Language (SQL) allows users to
manage, update, and retrieve data in a relational database.
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. Applications appropriate for an object-oriented
database include a multimedia database, a groupware database, a computer-aided
design (CAD) database, a hypertext database, and a hypermedia
database. Object-oriented databases often use an object query language (OQL)
to manipulate and retrieve data.
A multidimensional database stores data in
dimensions. These multiple dimensions, sometimes
known as a hypercube, allow users to access and analyze any view of the database data. No standard query language
exists for multidimensional databases. One a application
that uses multi dimensional databases is a data warehouse, which is a huge database
that stores and manages the data required to analyze historical and current transactions.
A smaller version of a data warehouse is the data mart,
which contains a database that help a specific
group or department make decisions.
8.
How Are
Web Databases Accessed?
To access data in a Web database, you fill in a form or enter
search text on a Web page, which is the front end to the database. A Web
database usually resides on a database server, which is a computer that
stores and provides access to a database. One type of program that manages the
sending and receiving of data between the front end and the database server is
a CGI (Common Gateway Interface) script.
9.
What Are the Responsibilities of Database
Analysts and Administrators?
A database analyst (DA), or data modeler,
focuses on the meaning and usage of data. The DA decides on the placement of fi
elds, defines data relationships, and identifi es users’ access privileges.
A database administrator (DBA) requires a more
technical inside view of the data. The DBA creates and maintains the data
dictionary, manages database security, monitors database performance, and
checks backup and recovery procedures. In small companies, one person often is
both the DA and DBA. In larger companies, the responsibilities of the DA and
DBA are split among two or more people.
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