Database Management Systems Explained

Database Management

Sumesh Koyon

Objectives Overview

Define the
term, database, and
explain how a database
interacts with data and
information

Describe the qualities of
valuable information

Discuss the terms
character, field, record, an
d file

Describe file maintenance
techniques (adding
records, modifying
records, deleting records)
and validation techniques

Differentiate between a
file processing approach
and the database
approach

Discuss the functions
common to most
database management
systems

Support Organization With IT

2

Objectives Overview
Data dictionary, file
retrieval and
maintenance, data
security, and backup
and recovery

Describe characteristics
of relational, objectoriented, and
multidimensional
databases

Explain how to access
Web databases

Discuss the
responsibilities of
database analysts and
administrators


3

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.


4

Databases, Data, and Information
• Computers process data in a database into information.
• A database at a school, for example, contains data about
students, e.g., student data, class data, etc.


5

Database Management System (DBMS)
• With database software, often called a database
management system (DBMS), users create a
computerized database; add, modify, and delete data in
the database; sort and retrieve data from the database;
and create forms and reports from the data in the
database.


6

Data Integrity
• Most organizations 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, an
organization 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.

7

Qualities of Valuable Information
• The information that data generates also is an important
asset.
• People make decisions daily using all types of information
such as receipts, bank statements, pension plan
summaries, stock analyses, transcripts, and credit
reports.
• At school, students use grade reports and degree audits
to make decisions.
• In a business, managers make decisions based on sales
trends, competitors’ products and services, production
processes, and even employee skills.

8

• To assist with sound decision making, information must
have value.
• For it to be valuable, information should be accurate,
verifiable, timely, organized, accessible, useful, and costeffective.


9

•
•
•
•

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.

10

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 student has an 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.


11

Records
• A record is a group of related fields. For example, a
student record includes a set of fields about one student.
• A primary key is a field that uniquely identifies each
record in a file.
• The data in a primary key is unique to a specific record.
• For example, the Student ID field uniquely identifies each
student because no two students can have the same
Student ID.


12

Files
• A data file is a collection of related records stored on a
storage medium such as a hard disk or optical disc.
• A Student file at a school might consist of thousands of
individual student records.
• Each student record in the file contains the same fields.
Each field, however, contains different data.


13

Files


14

Maintaining Data
• File maintenance refers to the procedures that keep data
current.
• File maintenance procedures include adding records
to, modifying records in, and deleting records from a file.


15

Adding Records
• Users add new records to a file when they obtain new
data.
• If a new student is admitted to the school, an admissions
department clerk adds a new record to the Student file.


16

Deleting Records
• When a record no longer is needed, a user deletes it from
a file.


17

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 analyzes
data, either as you enter it or after you enter it, to help
ensure that it is correct.
• For instance, when an admissions department clerk adds
or modifies data in a student record, the DBMS tests the
entered data.


18

File Processing versus Databases
• Almost all application programs use the file processing
approach, the database approach, or a combination of
both approaches to store and manage data.


19

File Processing Systems
• In the past, many organizations exclusively used file
processing systems to store and manage data.
• In a typical file 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.


20

• Data Redundancy — Each department or area in an
organization 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 a school, for example, the
Student file and the Student Schedule file both might
store the same students’ names and addresses.


21

• 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.


22

The Database Approach
• When an organization uses the database
approach, many programs and users share the data in
the database.
• A school’s database most likely at a minimum contains
data about students, instructors, schedule of classes, and
student schedules.
• The database does secure its data, however, so that only
authorized users can access certain data items.
• While a user is working with the database, the DBMS
resides in the memory of the computer.

23

The Database Approach


24

Data Dictionary
• A data dictionary contains data about each file in the
database and each field within those files.
• For each file, it stores details such as the file
name, description, the file’s relationship to other
files, and the number of records in the file.
• For each field, it stores details such as the field
name, description, field type, field size, default
value, validation rules, and the field’s relationship to
other fields.

25

File Retrieval and Maintenance
• A DBMS provides several tools that allow users and
programs to retrieve and maintain data in the database.
• To retrieve or select data in a database, you query it.
• A query is a request for specific data from the database.
• Users can instruct the DBMS to display, print, or store the
results of a query.
• The capability of querying a database is one of the more
powerful database features.


26

Query Language
• A query language consists of simple, English-like
statements that allow users to specify the data to display,
print, or store.
• Users can retrieve actual data in a query or display the
results of calculations performed on the data.
• Each query language has its own grammar and
vocabulary.


27

Data Security
• A DBMS provides means to ensure that only authorized
users access data at permitted times.
• In addition, most DBMSs allow different levels of access
privileges to be identified for each field in the database.
• These access privileges define the actions that a specific
user or group of users can perform.
• Access privileges for data involve establishing who can
enter new data, modify existing data, delete unwanted
data, and view data.

28

Backup and Recovery
• Occasionally a database is damaged or destroyed
because of hardware failure, a problem with the
software, human error, or a catastrophe such as fire or
flood.
• A DBMS provides a variety of techniques to restore the
database to a usable form in case it is damaged or
destroyed.


29

Backup and Recovery
• A backup, or copy, of the entire database should be
made on a regular basis. Some DBMSs have their own
built-in backup utilities. Others require users to purchase
a separate backup utility, or use one included with the
operating system.
• More complex DBMSs maintain a log, which is a listing of
activities that change the contents of the database.


30

Backup and Recovery
• A DBMS that creates a log usually provides a recovery
utility. A recovery utility uses the logs and/or backups to
restore a database when it becomes damaged or
destroyed.
• Continuous backup is a backup plan in which all data is
backed up whenever a change is made. This backup
technique can cost more than other backup strategies
but is growing in popularity because of its benefits.


31

Relational, Object-Oriented, and Multi
dimensional Databases
• 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
– multidimensional

32

Relational Databases
• 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.


33

• A relational database uses terms different from a file
processing system.
• A developer of a relational database refers to a file as a
relation, a record as a tuple, and a field as an attribute.
• A user of a relational database, by contrast, refers to a
file as a table, a record as a row, and a field as a column.


34



35

SQL Structured Query Language (SQL)
• Structured Query Language (SQL) is a popular query
language that allows users to manage, update, and
retrieve data.
• SQL has special keywords and rules that users include in
SQL statements.
• Eg:
– Select * from table_name;


36

Object-Oriented Databases
• 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 Student object, for example, might contain data about
a student such as Student ID, First Name, Last Name,
Address, and so on.


37

Object-Oriented Databases
• Object-oriented databases have several advantages
compared with relational databases: they can store more
types of data, access this data faster, and allow
programmers to reuse objects.
• An object oriented database stores unstructured data
more efficiently than a relational database.


38

Object Query Language
• Object-oriented databases often use a query language
called object query language (OQL) to manipulate and
retrieve data.
• OQL is similar to SQL.
• OQL and SQL use many of the same rules, grammar, and
keywords.
• Because OQL is a relatively new query language, not all
object databases support it.


39

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
analyse any view of the database data.
• No standard query language exists for multidimensional
databases.
• Each database uses its own language.
• Most are similar to SQL.

40

Data Warehouses
• A data warehouse is a huge database that stores and
manages the data required to analyse historical and
current transactions.
• Through a data warehouse, managers and other users
access transactions and summaries of transactions
quickly and efficiently


41

Web Databases
• 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, photos, movies, videos, local and national
weather, sporting events, and legislative information.


42

Web Databases
• Much of this and other information exists in databases
that are stored on the Web or are accessible through the
Web.
• Some Web databases are collaborative databases, where
users store and share photos, videos, recordings, and
other personal media with other registered users


43

Web Databases


44

Database Administration
• Managing a company’s database requires a great deal of
coordination.
• The role of coordinating the use of the database belongs
to the database analysts and administrators.
• To carry out their responsibilities, these IT (information
technology) professionals follow database design
guidelines and need cooperation from all database users.


45

Database Design Guidelines
•
•
•
•

Determine the purpose of the database.
Design the tables or files.
Design the records and fields for each table or file.
Determine the relationships among the tables or files.


46

Role of the Database Analysts and
Administrators
• The database analysts and administrators are
responsible for managing and coordinating all
database activities.
• The database analyst (DA) decides on the proper
placement of fields, defines the relationships
among data, and identifies users’ access
privileges.


47

Role of the Database Analysts and
Administrators
• The database administrator (DBA) requires a
more technical inside view of the data.
• The DBA creates and maintains the data
dictionary, manages security of the
database, monitors the performance of the
database, and checks backup and recovery
procedures.


48

Role of the Employee as a User
• Employees should learn how to use the data in
the database effectively.
• The amount of information available often
amazes first-time database users.
• Instant access to information helps employees
perform their jobs more effectively.
• Today, employees access databases from their
office desktop computers, notebook
computers, or even smart phones and other
mobile devices.

49

Objectives Overview

Define the
term, database, and explain
how a database interacts
with data and information

Describe the qualities of
valuable information

Discuss the terms
character, field, record, and
file

Describe file maintenance
techniques (adding
records, modifying
records, deleting records)
and validation techniques

Differentiate between a file
processing approach and
the database approach

Discuss the functions
common to most database
management systems


50

Objectives Overview
Data dictionary, file
retrieval and
maintenance, data
security, and backup
and recovery

Describe characteristics
of relational, objectoriented, and
multidimensional
databases

Explain how to access
Web databases

Discuss the
responsibilities of
database analysts and
administrators


51

Database Management Systems Explained

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