Download Database Processing Systems

Module 5 Part 1
Introduction To Database
Module Objectives
• At the end of the module, students should be
able to:
– describe the needs to database and define basic
database terminologies.
– explain the differences between file and database
processing systems.
– describe the DBMS and its common models 
relational, network, hierarchical and object-oriented.
– Describe the concept of data integrity
– describe the parts of DBMS software including DDL,
DML, query language and report generator.
– describe the importance and needs to a database
security, backup and recovery.
Needs to a Database
• The purpose of a database is to help people keep track
of things.
• A database is like a file-cabinet, to store information.
– Folders in a file cabinet can be arranged to hold data in some
useful order, so are the records in a database  we can search
for specific information, manage the information such as add,
modify, delete and so on.
• Database can be defined as a set of information
related to a specific application.
• The classical database applications  the tracking of
items like orders, customers, jobs, employees, phone
calls, or other items of interest to a business person.
Basic Database Terminologies
• Entity  a person, place object, event or concept in the user
environment about which the organization wishes to maintain data
– Some examples entities are Employee, Student, Building,
Registration, Account, Course
• Table / File  a collection of related records, the storage entity for a
database (Figure 5.1)
– made up of records that contain data about a single thing, such as a
person or a sales transaction.
Figure 5.1: A Table
Basic Database Terminologies
• Record  set of fields containing data about a person, place, or
thing, a unit within the table (Figure 5.2).
– Each record in a table contains related information about an entity.
Figure 5.2: A Record
• Field  a smaller unit within a record that contains a fact / attribute
about the entity.
– E.g. in customer record, one field might contain a customer’s name,
another field might contain the customer ID.
Basic Database Terminologies
• Key  used to order, identify and retrieve the records in the
database.
– defined from one or more fields from a table(s).
– E.g. Key in table Customer is CustomerID.
• Primary key is the unique identifier for a particular record, no two
records can have the same key value.
• Secondary key is defined by information from one or more other
fields within the database.
– E.g. A secondary key is created from the FirstName and LastName
fields.
– A secondary key differs from a primary key in that it allows multiple
occurrences of the same table.
Files and Databases
• Traditionally, information systems were
developed with a file processing approach
• Database approach creates separate files
for each entity
File Processing Systems
• Groups of records are stored in separate files
–
–
–
–
–
each application had its own file
Data was not shared among applications
Separate programs process separate data.
Allow only one file at a time to be processed.
The information stored in one file cannot be linked to other files. (Figure 5.3)
Employee
Processing
Application
Employee
File
Employee File User
Payroll
Processing
Application
Payroll File User
Figure 5.3: Two File-Processing System
Payroll
File
File Processing Systems
• The limitations:
– Data are separated and isolated
– Data are often duplicated
– Application programs are dependent on file
formats
– Files are often incompatible with one another
– It is difficult to represent data in user’s
perspectives
Database Processing Systems
• Database technology was developed to overcome the limitations of
file-processing systems.
• Database processing programs will call DBMS (database
management system) to access the stored data.
• DBMS is used to define, create, maintain and provide controlled
access to the database. (Figure 5.4)
Employee
Processing
Application
DBMS
Employee File
User
Figure 5.4: Relationship between application program and DBMS
Database Processing Systems
• The advantages:
• Data independence - reduces the dependency of programs on file
formats. All record formats are stored in the database itself and they
are accessed by the DBMS, not by application programs. This will
also minimizes the impact of data format changes on application
programs.
• Integrated data - All data is stored in a single facility called
database and it will maintain the consistency of the data in all
applications.
• Reduced data redundancy - redundancy level is minimal when
data is kept in only one place, less opportunity for discrepancies
among multiple copies of the same data item.
• Data security - data security in database package is to protect the
data from unauthorized individuals
Database Models
• 4 common types of database models
(Figure 5.5.)
i. Hierarchical database
Traditional database models developed to store
ii. Network database
text and numeric data
iii.Relational database
iv.Object-oriented database
Hierarchical
Network
Relational
Figure 5.5: DBMS organizations
Object-oriented
i). Hierarchical Model
• Arranges data in hierarchical “parent-child”
relationship
– Each parent record can have many child
records
– Each child record has only one parent record
• Complex and inflexible
ii). Network Model
• Arranges data in complex network of
“parent-child” relationships
– Each parent record can have many child
records
– Each child record can have many parent
records
• Complex and inflexible
iii). Relational Model
• Data organized in
table format
– Columns represent
fields
– Rows represent
records
• Tables related by
primary/foreign key
relationship
• Most current
database
development uses
this model
iv). Object-Oriented Model
• Designed to deal with complex data types
• Focuses on the object
– An object represents an entity
– Represents data about that entity and the types of operations
that change that entity
• Today newest type of database structure.
• In an OO-database, the result of a retrieval operation is
an object of some kind, such as a document.
• Within this object are miniprograms that enable the
object to perform tasks, such as displaying a graphic.
• OO-database can incorporate sound, video, text and
graphics into a single database record.
Data Integrity
• Refers to the degree to which data is
accurate and reliable
• Integrity constraints – set of rules that all
data must follow
– If integrity constraints are not followed, the
data is unreliable
Integrity Constraints
• Define acceptable values
for a field
– For example, the value of a
month cannot be greater than
12
• Primary keys cannot be
duplicated (unique)
• Foreign keys cannot be
used unless they exist as a
primary key
– A SalesID that is used in the
customer table must exist as
a primary key in the
salesperson table
Database Management
• A Database Management System (DBMS) 
allows you to create a database and enter,
modify, and retrieve data as needed
• Nowadays, the features and functions of many
DBMS have grown to the point that the DBMS
itself can process the application.
– They contain report writers, form generators that can
be integrated into an application.
• available at all levels
– Sophisticated systems for a mainframe environment
– Inexpensive, easy-to-use personal computer systems
Database Features
1.
2.
3.
4.
5.
6.
Data dictionary
Data maintenance
Data retrieval
Concurrency control
Security
Backup and recovery
1. Data Dictionary
• Stores data about the tables and fields
within the database
– For each table, it stores the table name and
relationships to other tables
– For each field, it records information about
that field
• Also called a catalog
2. Data Maintenance
• Three basic operations
– Adding new data
– Modifying existing data
– Deleting data
• Two methods for performing operations
– Interacting directly with the DBMS
– Using programs to access the data using
special commands
3. Data Retrieval
•
•
Involves extracting the desired data
Two primary forms of data retrieval
a) Queries
b) Reports
a) Queries
•
•
You present a set of criteria; the DBMS
selects matching data from the database
Use a query language
i.
Structured Query Language (SQL) is
supported by most relational databases
ii. Query-by-example (QBE) uses a graphical
interface to generate the SQL
iii. Display results in a table-like grid
b). Reports
• Provide a formatted
presentation of data
from the database
– Allow you to group
reports and total by
group, if desired
– Normally contain more
data than queries
• Reports are designed
with a report generator
4. Concurrency Control
• Manages simultaneous database users
– If several users tried to update the same
record at the same time, updates might not be
processed correctly
• Employs a record-locking scheme
– Once a user accesses a record, it is locked
until the first update is complete
5. Security
• Many security features are built into most DBMS
software
– Users can be required to enter a user ID and
password
– Each user ID may have different access to the data
• Read-only – permits the user to look at the data but not
change it
• Update – permits the user to make changes to the data
• No privileges – user can not read or update the data
6. Backup and Recovery
• Backup – a copy of the database
– Backups should be made periodically
• Recovery – replaces a damaged database
with the good backup
Parts of DBMS Software
• Data Definition Language (DDL)
o Is used to define the structure or the schema of the database.
o The structure outlines the data to be included in the database.
o Each field in a record must be defined with a name, a field
length and a type.
• Data Manipulation Language (DML)
o Includes all the commands that enable the user to manipulate
and use the database.
o User can view the data, add new records, delete records, sort
the records and modify selected fields in a record.
Parts of DBMS Software
• Query Language
o Enables user to ask specific questions of the database.
o The most popular query language is Structured Query
Language (SQL) and today, it is used in database management
systems on any platforms
• Report Generator
o The report generator helps the user to design and generate
reports and graphs in printed form.
o Some of the features that are easy to include with the report
generator are: report headings, column headings, page numbers
and totals.