82 terms

Discovering Computers Ch. 10

What is a database?
a collection of data organized in a manner that allows access, retrieval, and the use of that data.
database software
often called a database management system (DBMS), allows users to create a computerized database: add, change, 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 is
processed data; that is, it is organized, meaningful, and useful
information can be in the form of
documents, audio, images, and video
for information to be valuable, it should be
accurate, verifiable, timely, organized, accessible, useful, and cost-effective
accurate informatiion 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
Why is data important to an organization
data is used to generate information, many companies 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 evtered in a database must have integrity
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 smalles unit of data a computer can process
eight bits grouped together in a unit form
a byte
each byte represents
a single character, which can be a number, letter, 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 fields
a data file is
a collection of related records stored on a storage medium such as a hard disk, CD, or DVD
file maintenance
refers to the procedures that keep data current
file maintenance procedures
include adding records when new data is obtained, changing records to correct inaccurate data or to update old data with new data, and deleting records when they no longer are needed
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
a validity check
analyzes entered data 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 chec, and a check digit
in a file processing system
each department or area within an organization has its own set of data files
the records in one file may not
relate to the records in any other file
two major weknesses of file 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 has these benefits:
reduces data redundancy, improves data integrity, shared data, permits easier access, and reduces development time
a database has these downsides:
can be more complex than a file processing system, requiring special training and more computer memeory, storage, and processing pwer than file processing systems
data in a database also more
vulnerable than data in file processing systems
database management system
data dictionary
sometimes called a repository, contains data about each file in the database and each field in those files
DBMS offers several methods to
maintain and retrieve data
methods of maintaining and retrieving data in a DBMS include
query by example, forms, and report generators
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 graphical user interface that assits users with retrieving data
sometimes called a, data entry form, is a window on the screen that provides areas for entering or changing data
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
the supply security, most DBMSs can
identiry different levels of access privileges
access privileges
define the actions a specific user of group of users can perform for each field in a database
if a database is damages or destroyed
a DBMS provides techniques to return the database to a usable form
a backup is
a cory of the database
a log is
a listing of activities that change 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 follforward
the DBMS used the log to reenter changes made to the database since the last save or backup
in a rollback
the DBMS uses the log to undo any changes made to the database during a certain period
continuous backup
a backup plan in which all data is backed up whenever a change is made
a data model consists of
rules and standards that define how the database organizes data
three popular data models are
relational, object-oriented, and multidemensional
relational database
stores data in tables that consists of rows and columns
a relational database developer refers to
a file 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 field as a column
a relationship is
a conneciton within the data in a relational database
structured query language (SQL)
allows users to manage, update, and retrieve data
and 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 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 Web database
object-oriented databases often use
an object query language (OQL) to manipulate and retrieve data
a multidemensional database
stores data in demisions
multiple demensions, sometimes called a hypercube, allow users to
access and analyze any view of the database data
one application that uses multidimensional databases is
a data warehouse
a data warehouse is
a huge database that stores and manages the data required to analyze historical and current transactions
no standard query language exists for
multidimensional databases
a smaller version of a data warehouse is
the data mart, which contains a database that helps a specific group or department make decisions
o 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
a database server is
a computer that stores and provides access to a database
one type or program that manages the sending and receiving of data between the front end and the database server is a
CGI (Common Gateway Interface) script
database analyst (DA)
or data modeler, focuses on the meaning and usage of data
DA decides on
the placement of fields, defines data relationships, and identifies access privileges
a database administrator (DBA)
requires a more technical view of the data
the DBA
creates and maintains the data dictionary, manages database security, monitors database performance, and check 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 amont two or more people