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

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

valudation

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

DBMS

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

form

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