Introduction to Database System
By: Abenet A. @2022
Course Overview
 In this course we will cover
the following main topics:
-
Database systems
Database models
SQL
Normalization
Database design
File Organization
 Practical/Lab sessions
 Will start on June 22,
2022
 Ms-access
 SQL
⁃ creating a database
⁃ querying a database
2
Chapter One
Chapter Outlines:
⁃ Introduction to Database Systems
⁃ Manual file handling approaches
⁃ File based vs. Database approach
⁃ Characteristics of the Database
Approach
⁃ Users and actors of Database
system.
Chapter Objectives:
 Understanding the limitations of
manual file handling methods
 The characteristics of file-based
systems.
 The problems with the file-based
approach.
 The
meaning
of
the
term
database.
 Some common uses of database
systems
3
Introduction
Data, information, information System:
• Data: is a collection of raw facts and figures
• Information: is a processed data in the form that is meaningful to
the user.
• Information System is a system that:
⁃ Receives data and instruction
⁃ Processes the data as per the instruction
⁃ Produces output
⁃ Stores data/information for future use
4
Introduction…
Information System, Organization, and database system
• Information System doesn’t exist without organization. That is,
organization of data is necessary if data is voluminous.
• Information System is a support system for the organizational
activity to achieve a certain goal.
• A database system is basically a computerized record keeping
system. Users of the database can perform a variety of
operations. Such as:
– Adding new data to empty file
– Adding new data to existing file
– Retrieving data from existing file
– Modifying data to existing file
– Deleting data from existing file
– Searching for target information
5
Introduction…
Data handling approaches:
– Data management passes through the different levels of
development along with the development in technology and
services.
– These levels could be best described by categorizing the levels into
three levels or types of development/approach.
– Even though there is an advantage and a problem overcome at
each new data handling approach/level, all methods or
approaches of data handling are in use to some extent.
– The major three approaches/levels are discussed as follows in this
chapter below:
6
Introduction: Why we need to Study Databases?
 Databases are useful, because of:
─ Many computing applications deal with large amounts of information(Large
volumes of data can be stored in one place.)
─ Database systems give a set of tools for storing, searching and managing this
information
 Databases in IT
─ Databases are a ‘core topic’ in Information Technology(IT fields)
─ Basic concepts and skills with database systems are part of the skill set you
will be assumed to have as a IT graduate
─ Databases are everywhere (i.e. lots of job opportunities).
• E.g. Google ... Database research offers many exciting
opportunities.
7
Introduction: Why Study Databases?...
 Databases are useful, because of:
─ Today, Databases are essential to every business.
─ They are used to maintain internal records, to present data to customers and clients
on the World-Wide-Web, and to support many other commercial processes.
─ Database systems are designed to manage large data set in an organization.
─ A database is typically designed so that it is easy to store and access information. A
good database is crucial to any company or organization.
─ This is because the database stores all the pertinent details about the company such
as employee records, transactional records, salary details etc.
─ To organize information, To be able to get reports from data
─ To protect data – the security features of a database allow you to specify who has
access, what data they can see and what they can do with the data
─ To be able to share data
8
Why use Databases?
⁃ Data is a valuable corporate resource which needs adequate,
accuracy, consistency and security controls.
⁃ The centralized control of data means that for many
applications the data will already exist, and facilitate quicker
development.
⁃ Data will no longer be related by application programs, but
by the structure defined in the database.
⁃ Database systems give a set of tools for storing, searching
and managing this information.
⁃ Easier to maintain systems
9
Introduction to Database System
 Database can represents some features of the real world entity, sometimes called
the mini-world.
─ Database: is a collection of logically related elements.
o But a random collection of data cannot correctly be referred to as a database.
─ Data: is known raw facts and figures that can be recorded and have an implicit
meaning.
─ Mini-world: Some part of the real world about which data is stored in a
database.
o Example: student grades and transcripts at a university.
A Manufacturing Company with product data
– A Bank with account data
– A Hospital with patients
– A University with Students
– A government with planning data
–
.
10
Introduction to Database System
What is a database system?
•
It is a computerized record keeping system, which stores related data in an organized way.
•
The overall purpose of a database system is to store information and to allow users to add,
delete, retrieve, search, query and update that information upon request.
•
store information and allow users to add, delete, retrieve, search, query and
update that information upon request on demand.
•
Database System: The DBMS software together with the data itself.
•
•
Sometimes, the applications are also included.
Database System:
– The DBMS software together with the data itself.
» Sometimes, the applications are also included.
Note: Database System (DBS) contains:
•
The Database + The DBMS + Application Programs (what users interact with)
11
What is a database system?
• It is a computerized record keeping system, which stores related data
in an organized way.
• The overall purpose of a database system is to store information and
to allow users to add, delete, retrieve, search, query and update that
information upon request.
•
The information concerned can be anything that is deemed to be of
significance to the individual or organization the system is intended to
serve.
• That is, needed to assist in the general process of running the business
of that individual or organization.
12
Components of a Database System…
• A database system involves four major components, namely, data,
hardware, software and users and designers of database.
• A brief discussion will follow on each of these components.
 Data:
– The actual data stored in the database system may be stored
as a single database or distributed in many distinct files and
treated as one.
– Is the system a single-user or multi-user one?
– How are we going to achieve the utmost possible performance
concerning the data storage and maintenance?
– What other benefits or drawbacks do we expect as the result
of placement or structure of the database?.
– These and similar issues might be concerned with the way the
data stored in the system.
13
Components of a Database System…
 Hardware:
– This portion of the system consists of secondary storage media
(disks, tapes and optical media) that are used to hold the stored
data and associated device controllers (hard disk controller, etc.);
and the processor(s) and associated main memory that are used to
support the execution of the database system software.
 Software:
– This is the software, Database Management System (DBMS) that is
responsible for the overall management of communications
between the user and the database.
– It is found between the data and the users, which, in other words,
means the data is entirely covered or shielded by the DBMS
software.
– The DBMS provides facilities for operating on the database.
– This is the most important software component in the overall
system that allows the user to interact with the data.
 Users and Designers of Database:
– As people are one of the components in DBS environment, there
are group of roles played by different stakeholders of the
14
designing and operation of a database system.
Introduction to Database System…
• Database can be designed, built, and populated with
data for a specific purpose.
• A database has an intended group of users and some
predetermined applications in which these users are
interested.
• However, data management passes through the different
levels of development along with the development in
technology and services.
• These levels could best be described by categorizing the
levels into three levels of development.
• Even though there is an advantage and a problem
overcome at each new level, all methods of data handling
are in use to some extent.
15
Introduction to Database System…
• Data management passes through the different levels of
development along with the development in technology
and services.
• These levels could best be described by categorizing the
levels into two levels of development.
• Even though there is an advantage and a problem
overcome at each new level, all methods of data handling
are in use to some extent.
• Methods of data handling are :
• Manual Approach
• Computerized or file based Approach
• Data base Approach
- The first one is Manual File Handling Approach
16
1. Manual File Handling Systems
• In the manual approach, data storage and retrieval follows the primitive and
traditional way of information handling where cards and papers are used for
the purpose.
• Typing the data on paper and put in a file cabinet.
• This approach works well if the number of items to be stored is small.
• In the manual approach, the data storage and retrieval will be performed using
human labour.
– Files for as many event and objects as the organization has are used to
store information.
– Each of the files containing various kinds of information is labelled and
stored in one or more cabinets.
– The cabinets could be kept in safe places for security purpose based on the
sensitivity of the information contained in it.
– Insertion and retrieval is done by searching first for the right cabinet then
for the right the file then the information.
– One could have an indexing system to facilitate access to the data
17
Manual File Handling Systems
 A manual file handling systems can operated by hand, so it require human effort .
 Some examples of manual file management systems, might start by building a file with the
following structure:
• e.g. Personal Calendar
o Let us also build our address book:
o This calendar is easy to deal with.
18
Limitations Of Using Manual File Handling System
 Some limitations of using manual file handling system:
 Problem of Data Organization
• Suppose we want to cancel one of our appointments
• Two conceptual “entities”, address and calendar with a relationship between them,
linking people in the calendar to their contact information.
• This link could be based on something as simple as the person's name
 Problem of Efficiency
• Size of your personal address book is probably less than one hundred entries, but
there are things we would like to do quickly and efficiently.
– “Give me all appointments on 10/28”
– “When am I next meeting Dr. Dawit?”
– What would happen if you were using a business calendar with hundreds of
thousands of entries?
19
Limitations Of Using Manual File Handling System…
Example 1: In the University
• Students file is kept in the Registrar, Faculty, Dean of Students, Library.
• Each has its own purpose of keeping the files.
• When registrar officer wants to look for a certain student, he/she go to the student file and
search through the system starting from the first entry until he/she find what he/she wants.
• This may work well if the number of items to be stored is small.
• Questions:
– If you change your department does the dean of students know??
– If you change your dormitory, does the library know??
• Necessary information you keep: Name, age, sex, department, dormitory, etc…
•
You might want to compile possible information:
– Give me all females in the Department of Information Technology
– Give me all students over the age of 23
– Give me all students who have G.P.A of 3.0 or above & G.P.A less than 2.5
– Give me all students who live in building 205 and who are in department of IT.
20
Limitations Of Using Manual File Handling System…
 Example 2: In the real state agent
 Consider yourself as a person working at the company
• What type of house do you have for sale?
• What type of house do you have for rent?
• What three bedroom properties do you have for sale?
• What one bedroom properties do you have for sale with a garden and a garage?
• What flats do you have for rent within 3 miles of the city center and with two bed
rooms
• How many apartments to you have with three bed rooms?
• Which one of the houses is explicitly for office use?
 Necessary information you might keep:
• Type of house, no. of bed rooms, no. of toilets, garden, service department, distance, all
purpose?
21
Limitations Of Using Manual File Handling System…
 Example 3: In the Library
• How do you register in the
library?
• How does the librarian know the
book is its property?
• How do you borrow a material?
the Process involved??
• How do you return a material??
• What if you do not return a
material?
• What if you lose a pocket?
• How does the library decide which
books to get more
 Option : If the no. of users are small, it is easier to handle.
22
Limitations Of Using Manual File Handling System…
 Generally, the Problems/ Limitations of the Manual approach are:
• Prone to error,
• difficult to update, retrieve, integrate
• You have the data but it is difficult to compile the information
• Limited to small size information and
• cross referencing is difficult
• Data loss: Due to damaged papers or unable to locate it.
• Redundancy: Multiple copies of the same data within the
organization.
• Inconsistency: Modifications are not reflected on all multiple
copies
23
2. Computerized/file based Approach
• An alternative approach of data handling is a computerized way of dealing with
the information or data.
• The computerized approach could also be either decentralized or centralized
base on where the data resides in the system.
• In this approach every information or data is stored in the computer unlike
manual approach.
• That means in order to perform any activity, we use computer during
computerized approach like storage and retrieval processing.
 In consequence to overcome the above (Manual file handling system) limitations,
two computerized approaches are developed:
File based approach  decentralized
Database approach  centralized
24
Computerized / File-Based Approach…
 After the introduction of Computer for data processing to the business
community, the need to use this device for data storage and
processing increase.
 File based data handling approaches were an early attempt to
computerize the manual filing system.
 There were, and still are, several computer applications with file based
processing used for the purpose of data handling.
 Even though the approach evolved over time, the basic structure is still
similar to manual approach but not identical.
 File-Based Approach: is a collection of application programs that
perform services for the end-users, such as the production of reports .
25
Computerized /File-Based Approach …
File
based
approach
is
the
decentralized
computerized data handling method.
In this approach, each program defines and manages
its own data.
This approach is used to develop a program or a
number of programs for each different application.
Data is stored in one or more separate computer files
26
Computerized File-Based Approach …
• The characteristics of FBA are:
– This approach is the decentralized computerized data handling method.
That means data is stored in different place inside the computer.
– A collection of application programs perform services for the end-users.
In such systems, every application program that provides service to end
users defines and manages its own data.
– Such systems have number of programs for each of the different
applications in the organization.
– Since every application defines and manages its own data, the system is
subjected to serious data duplication problem.
– File, in traditional file based approach, is a collection of records which
contains logically related data.
27
Limitations of the File Based approach
• As business application become more complex demanding more
flexible and reliable data handling methods, the shortcomings of the
file based system became evident.
• These shortcomings include, but not limited to:
1. Separation or Isolation of Data:
– Available information in one application may not be known.
– Data Synchronisation is done manually.
– When data is isolated in separate files, it is difficult to access
data that should be available.
– This is because; there is no concept of relationship between
files.
• Therefore, we need to create a temporary file for the
participating files.
28
Limitations of the Traditional File Based approach
2. Duplication or redundancy of data:
– This is concerning with storage of similar information in multiple
files.
• The following are some of the disadvantage of redundancy:
– It costs time and money to enter the data
– It takes up additional storage space (memory space)
3. Inconsistency:
 this is loss of data integrity.
• For instance, if modification in the child table is unable to be
reflected on the parent table.
4. Limited data sharing: every application maintains its own data.
5. Lengthy development and maintenance time
29
Limitations of the Traditional File Based approach
6. Incompatible file formats:
– Incompatible file formats or data structures: (e.g. “C” and COBOL)
between different applications and programs creating inconsistency
and difficulty to process jointly.
– The structure of file is dependent on the application programs.
Incompatibility of files makes them difficult to process jointly.
• Example: consider two files with in the same enterprise but in
different departments, or in different branches: If the first file
is constructed using COBOL and the second file is written using
C++, then there will be a problem of integrity.
7. Fixed query processing: which is defined during application development
30
Limitations of the Traditional File Based approach...
8. Data dependency:
– on the application- data structure is embedded in the
application; hence, a change in the data structure needs to
change the application as well.
– Changes to an existing structure are difficult to make.
•
Example: change in the size of Student Name (from 20 characters to 30
characters) requires a new program to convert student file to a new
format.
– The new program opens original student file, open a temporary file, read
records from original student file and write to the temporary file, delete the
original student file and finally rename the temporary file as student file.
– It is time consuming and Prone to error.
31
Limitations of the Traditional File Based approach…
 Data is then processed by computer programs – applications
 The Figure in below shows that how different applications have their own copy of
the files they need in order to perform out an activities for which they are
responsible.
32
Limitations of File-Based systems…
 Keeping organizational information using a file system has a number of major
disadvantages:
 Data redundancy and inconsistency
• Since different programmers create the files and application programs over a
long period, the various files are likely to have:
─ different structures/ formats,
─ the programs may be written in several programming languages,
─ duplication of information in different files
o The same data is held by different programs
o E.g. The address and telephone number of a particular customer may appear
in a file that consists of Sale records and in a file that consists of contract
records.
 This redundancy leads to higher storage and access cost.
33
Limitations of File-Based systems…
 In addition, it may lead to data inconsistency; that is, the various copies of the
same data may no longer agree.
o E.g. , a changed customer address may be reflected in Sale records but not
elsewhere in the system.
 Difficulty in accessing data
 Suppose that one of the bank officers needs to find out the names of all
customers who live within a particular postal-code area.
• The officer asks the data-processing department to generate such a list.
• Because the designers of the original system did not anticipate this request,
there is no application program on hand to meet it.
• There is, however, an application program to generate the list of all
customers.
• The bank officer has now two choices:
⁃ either obtain the list of all customers and extract the needed
information manually or
⁃ ask a system programmer to write the necessary new application
34
program to carry out each new task
Limitations of File-Based systems…
• The point here is that conventional file-processing environments do not
allow needed data to be retrieved in a convenient and efficient manner.
• More responsive data-retrieval systems are required for general use.
 Separation and isolation of Data
 Each program maintains its own set of data.
• Users of one program may be unaware of potentially useful data
held by other programs.
 Because data are distributed in various files, and files may be in
different formats, writing new application programs to retrieve the
appropriate data is difficult.
35
Limitations of File-Based systems…
 Integrity problems
• Integrity constraints
• Inflexible to add new constraints or change existing ones
• The data values stored in the database must satisfy certain types of consistency
constraints.
o E.g, the balance of certain types of bank accounts may never fall below a
prescribed amount (say, 25 birr).
• Developers enforce these constraints in the system by adding appropriate code in the
various application programs.
• However, when new constraints are added, it is difficult to change the programs to
enforce them.
• The problem is compounded when constraints involve several data items from different
files.
36
Limitations of File-Based systems…
 Atomicity of updates
• A computer system, like any other mechanical or electrical device, is subject to failure.
• In many applications, it is crucial that, if a failure occurs, the data be restored to the
consistent state that existed prior to the failure.
o E.g., Transfer of birr 50 from account A to account B should either complete or not happen
at all
• If a system failure occurs during the execution of the Program, it is possible that the birr 50
was removed from account A but was not credited to account B, resulting in an inconsistent
database state.
• Clearly, it is essential to database consistency that either both the credit and debit occur, or
that neither occur.
• That is, the money transfer must be atomic-it must happen in its entirety or not at all.
Note: It is difficult to ensure atomicity in a conventional file-processing system.
37
Limitations of File-Based systems…
Concurrent access by multiple users
 For the sake of overall performance of the system and faster
response, many systems allow multiple users to update the data
simultaneously.
 Uncontrolled concurrent accesses can lead to inconsistencies
o E.g. Consider bank account A, containing birr 500.
• If two customers withdraw money (say 50 birr and 100
birr, respectively) from account A at the same time, the
result of the concurrent executions may leave the account in
an incorrect (or inconsistent)state.
38
Limitations of File-Based systems…
 Suppose that the programs executing on concern of each withdrawal read the
old balance, reduce that value by the amount being withdrawn, and write the
result back.
─If the two programs run concurrently, they may both read the value 500 birr,
and write back 450 birr and 400 birr, respectively.
─Depending on which one writes the value last, the account may contain either
450 birr or 400 birr, rather than the correct value of $350.
 To guard against this possibility, the system must maintain some form of
supervision.
 But supervision is difficult to provide because data may be accessed by many
different application programs that have not been coordinated previously.
39
Limitations of File-Based systems…
 Security problems
• Not every user of the database system should be able to access all the
data.
o E.g, in a banking system, payroll personnel need to see only that part
of the database that has information about the various bank
employees.
• They do not need access to information about customer accounts.
• But, since application programs are added to the file-processing
system for one specific routine, enforcing such security constraints is
difficult.
 These difficulties, among others, prompted the development of database
systems.
40
Limitations of File-Based systems…
• The limitations for the traditional file based data handling
approach arise from two basic reasons.
• Arose because:
– Definition of the data was embedded in the application program
which makes it difficult to modify the database definition easily ,
rather than being stored separately and independently
– No control over the access and manipulation of the data beyond
that imposed by the application programs.
– The most significant problem experienced by the traditional file
based approach of data handling is the “update anomalies”.
41
Limitations of File-Based systems…
 We have three types of update anomalies;
1. Modification Anomalies:
– a problem experienced when one or more data value is modified on
one application program but not on others containing the same data set.
2. Deletion Anomalies:
– a problem encountered where one record set is deleted from one application
but remain untouched in other application programs.
3. Insertion Anomalies:
– a problem experienced whenever there is new data item to be recorded, and
the recording is not made in all the applications.
– And when same data item is inserted at different applications, there could be
errors in encoding which makes the new data item to be considered as a totally
different object.
• Result:
The Database and Database Management System (DBMS).
42
3. Database Approach
 To become more effective, a new approach was required by the name
database approach.
oWhat emerged were the database and database management systems?
What is Database?
Database is a shared collection of logically related data (and a description of this
data), designed to meet the information needs of an organization.
─Logically related data collection - contains the important entities, objects,
attributes, and the relationships between these objects of an
organization's information.
─Description of the data – the system catalog (meta-data) provides
description of data to enable program data independence.
─Shared collection – can be used simultaneously by many departments,
sectors and users.
43
Database Approach…
• Database is a structured set of data held in a computer, especially
one that is accessible in various ways.
• “It is a set of information held in a computer”
– Oxford English Dictionary
• “One or more large structured sets of persistent data, usually
associated with software to update and query the data”
– Free On-Line Dictionary of Computing
• “Database is a collection of data arranged for ease and speed of
search and retrieval”.
. Dictionary.com
44
Database Approach…
• A database is a collection of related data in an organized way. Most of the time,
organization is in tabular form.
» E.g. book database
Call no
QA46
Title
Introduction to database
Author
Bahiru
Publisher
Addison Wesley
No of copies
15
 The organization of the database becomes necessary when the data is voluminous.
Otherwise, managing data will be very difficult.
• E.g. A Manufacturing Company with product data
»
A Bank with account data
»
A Hospital with patients
»
A University with Students
»
A government with planning data
45
Database Approach…
• A database is a collection of related data or information stored in a computer in
a systematic way, such that a computer program can read it to answer questions
• A database is a collection of organized data used by the applications/systems
of an organization.
• A database consists of:
» Data
» Relationships between the data
» Constraints on the data – or restrictions e.g. Quantity must be
greater than 0
» A schema – describes all the objects in the database (e.g. a
table has columns, a column has a data-type and a size)
46
Database Approach…
Thus in Database Approach:
– Database is just a computerized record keeping system or a kind of electronic
filing cabinet.
– It is a repository for collection of computerized data files.
– Since it is a shared corporate resource, the database is integrated with
minimum amount of or no duplication.
– It is a collection of logically related data where these logically related data
comprises entities, attributes, relationships, and business rules of an
organization's information.
– In addition to containing data required by an organization, database also
contains a description of the data which called as “Metadata” or “Data
Dictionary” or “Systems Catalogue” or “Data about Data”.
47
Database Approach…
– Since a database contains information about the data (metadata), it is called
a self-descriptive collection on integrated records.
– The purpose of a database is to store information and to allow users to
retrieve and update that information on demand.
– Database is designed once and used simultaneously by many users.
– Unlike the traditional file based approach in database approach there is
program data independence. That is the separation of the data definition
from the application.
– Thus the application is not affected by changes made in the data structure
and file organization.
– Each database application will perform the combination of: creating
database, reading, updating and deleting data.
48
Database Approach…
Databases example : Databases is everywhere!
₋ Web indexes
₋ Train timetables
₋ Library catalogues
₋ Airline bookings
₋ Medical records
₋ Credit card details
₋ Bank accounts
₋ Student records
₋ Stock control
₋ Customer histories
₋ Personnel systems
₋ Stock market prices
₋ Product catalogues
₋ Discussion boards
₋ Telephone directories
₋ and so on…
• so that databases touch all
aspects of our lives.
49
Database Approach…
Application areas of Database Systems:
₋ Banks
• Advanced Database Applications
1. Computer-Aided Design (CAD)
₋ HRM

₋ Stock Management
electrical
₋ Supermarket
₋ Library Systems
₋ Universities
₋ Etc
Stores
data
relating
design,
for
to
mechanical
example,
and
buildings,
airplanes, and integrated circuit chips.
2. Computer-Aided Manufacturing (CAM)
 Stores similar data to CAD, plus data
about discrete production.
3. Geographic Information Systems (GIS)
 GIS database stores spatial and temporal
information,
that
used
in
land
management and underwater exploration.
50
Database application program
What is Database application program?
• A software program that interacts with the database by
issuing an appropriate request (typically an SQL statement) to
the DBMS.
• The SQL (Structured Query Language), developed by IBM is
now the standard query language.
51
Basic Database Terminologies


Enterprise
⁃ an organization : A library, a bank, a university, etc.
Entity
⁃ Person, place, thing, or event (property of an entity)
⁃ An "object" in the real world that we are interested in:
Eg. The object student is an entity

Attribute (Field)
⁃ A character or group of characters (alphabetic or numeric), that has a specific meaning.
•
o E.g. Name, age, telephone, grade, sex, etc.
Reports
– A report is a database object that comes in handy when you want to present
the information in your database for any of the following uses:
• Display or distribute a summary of data. Archive snapshots of the
data. Provide details about individual records.
– If the query is a question...
...then the report is its answer
– Reports can be tailored to the needs of the data-user, making the
52
information they extract much more useful.
Basic Database Terminologies…
 File
⁃ A collection of related records.
o E.g, a file might contain data about customers; or students of a
certain department in a university.
 Database
• Collection of organized Files
 Queries
⁃ Queries are the information retrieval requests you make to the database
⁃ Your queries are all about the information you are trying to gather
• Fields
⁃ Database storage units
⁃ Generic elements of content
53
Basic Database Terminologies…
 Record : A logically connected set of one or more Attributes that describe a
person, place or thing. (Logically related data)
⁃ A simple table showing fields (columns) and records(rows):
• And as part of a MS Access database table
54
Advantages of the database approach
The advantages of a database approach over the traditional and
paper-based methods of record keeping will include the following:
⁃ Database systems offer solutions to all the above problems
– A database is a storage space for content / information (data)
⁃ Data independence/reduced maintenance
⁃ Improved data sharing
⁃ Increased application development productivity
⁃ Enforcement of standards
⁃ Improved data quality (constraints)
⁃ Better data accessibility/ responsiveness
⁃ Security, backup/recovery, concurrency
55
Some Common uses of Databases?

In a university, There is a database
₋ containing information about yourself, the course you are enrolled in, the dormitory
you have been given..
₋ containing details of Staff who work at the university at personnel, payroll, etc.

When you visit your library
₋ There may be a database containing details of the books in the library and details of
the users,

The database system handles activities such as
₋ Allowing a user to reserve a book
₋ Charging materials to users
₋ Notifying when materials are overdue : Sends out reminders to borrowers who have
failed to return books on the due data

The system will have a bar code reader to keep track of books and users.
56
Some Common uses of Databases?...
 In travel agencies
• When you make inquiries about a travel, the travel agent may access
databases containing flight details
o Flight no., date, time of departure, time of arrival
• Which passenger is in which flight??
 Insurance
• When you wish to take out insurance, there is database containing
o Your personal details: name, address, age
o information on whether you drink or smoke,
o Your medical records to determine the cost of the insurance
57
Some Common uses of Databases?...
 Supermarkets
• When you buy goods from some supermarkets, a database will be
accessed…..
o The checkout assistant will run a bar code reader over the
purchases –
o It is linked to a database application program, which uses the bar
code to find out the price of the item from a products database.
o It also reduces the number of such items in stock.
o If reorder level falls below the threshold, the system may
automatically place an order to obtain more stocks.
58
Benefits of the database approach
• Compactness
– since it is an electronic data handling method, the data is
stored compactly (no need for possibly voluminous paper
files).
• Speed:
– the machine can retrieve and change data faster than a
human can. In particular, ad hoc, spur-of-the-moment
queries
– (“Do we have more red screws than blue ones?”) can be
answered quickly without any need for time consuming
manual or visual searches.
– data storage and retrieval is fast as it will be using the
modern fast computer systems.
• Accuracy:
– timely, accurate and up-to-date information is available on
59
demand at any time.
Benefits of the database approach
• The foregoing benefits apply with even more force in a multi-user
environment where the database is likely to be much larger and
much more complex than in the single user case.
• In a multi-user environment the database system provides the
enterprise with centralized control of its data. The centralized
approach has the following advantages:
•
Data can be shared:
⁃ two or more users can access and use same data instead of
storing data in redundant manner for each user.
•
Improved accessibility of data:
⁃ by using structured query languages, the users can easily
access data without programming experience.
60
Benefits of the database approach…
•
Quality data can be maintained:
⁃ the different integrity constraints in the database approach will maintain
the quality leading to better decision making.
•
Transaction support can be provided:
⁃ basic demands of any transaction support systems are implanted in a full
scale DBMS.
•
Conflicting requirements can be balanced:
⁃ knowing the overall requirements of the enterprise the Database
Administrator (DBA) can structure the system so as to provide an overall
service that is best for the enterprise.
⁃ For example, a representation can be chosen for the data in storage that gives
fast access for the most important applications (possibly at the cost of poorer
performance for certain other applications).
61
Benefits of the database approach…
•
Inconsistency can be avoided:
⁃ controlled data redundancy will avoid inconsistency of the
data in the database to some extent.
•
If there are a number of files which store similar data elements
among other sorts of data then when a change is made to a
particular data (among the common ones) this change need to be
done throughout the system where there is such data stored.
•
This is not, often, the case. Some of the data might be updated
and others left as they are which results in inconsistent information
about the same phenomena.
62
Benefits of the database approach…
• Redundancy can be reduced:
⁃ isolated data is integrated in database to
decrease the redundant data stored at different
applications.
• In non database or non centralized systems each application or
department keeps its own private files.
• The files may hold common data elements that exist as part of the
enterprises data.
• This will lead to considerable redundancy in stored data, with
resultant waste in storage space.
– For example, a personnel application and an education records application
might both own a file that includes department information for employees.
• Note that, this is not to say we should eliminate all redundancies.
Sometimes there are sound reasons for maintaining several copies
63
of the same data.
Benefits of the database approach.
• Integrity can be maintained:
⁃ data at different applications will be integrated together
with additional constraints to facilitate shared data resource.
⁃ The problem of integrity is the problem of ensuring the data
in the database is accurate.
⁃ Inconsistency between two entries that represent the same
“fact” is an example of lack of integrity.
⁃ It is more serious in a multi-user environment where one user
may enter bad data and other users may go on working on
the updated data as if it were a correct one.
64
Benefits of the database approach.
• Security majors can be enforced:
⁃ the shared data can be secured by having different levels
of clearance and other data security mechanisms.
• Improved decision support:
⁃ the database will provide information useful for decision
making.
• Security restrictions can be applied:
⁃ Since the data is stored in one place/area all accesses to the data can be
regulated by the system through some defined rules built into the system.
⁃ The system ensures that the only means of access to the database is through
proper channels.
⁃ Different rules can be established for each type of access (retrieve, insert,
delete, etc.) to each of information to the database.
65
Benefits of the database approach.
• Standards can be enforced:
⁃ the different ways of using and dealing with data by
different unite of an organization can be balanced and
standardized by using database approach.
⁃ Standardizing data representation is particularly desirable
as an aid to data interchange or migration of data between
systems.
⁃ Likewise, data naming and documentation standards are also
very desirable as they facilitate data sharing and
understandability.
66
Benefits of the database approach…
• Less labour:
⁃ unlike the other data handling methods, data maintenance will not
demand much resource.
• Centralized information control:
⁃ since relevant data in the organization will be stored at one repository, it
can be controlled and managed at the central level.
• Transaction support can be provided:
⁃ basic demands of any transaction support systems are implanted in a full
scale DBMS.
• Centralized information control:
⁃ since relevant data in the organization will be stored at one repository, it
can be controlled and managed at the central level.
67
Limitations and risk of Database Approach
• Introduction of new professional and specialized personnel.
• Complexity in designing and managing data
• The cost and risk during conversion from the old to the new system
• High cost to be incurred to develop and maintain the system
• Complex backup and recovery services from the users
perspective
• Reduced
performance
due
to
centralization
and
data
independency
• High impact on the system when failure occurs to the central
system.
68
Characteristics of the Database Approach
 There are a number of features that distinguish the database approach from the
traditional approach of programming with files.
 In traditional file processing, each user defines and implements the files needed for a
specific software application as part of programming the application.
 In the database approach, a single repository of data is maintained that is defined once
and then is accessed by various users.
 The main characteristics of the database approach versus the file-processing approach are the
following:
 Self-describing nature of a database system: A DBMS catalog stores the description
of the database(The description is called meta-data).
• This allows the DBMS software to work with different databases.
69
Characteristics of the Database Approach…
 Insulation between programs and data:
⁃ Called program-data independence.
⁃ Allows changing data storage structures and operations without having to change the DBMS access
programs.
 Data Abstraction:
⁃ A data model is used to hide storage details and present the users with a conceptual view of the
database.
⁃ Programs refer to the data model constructs rather than data storage details
 Support of multiple views of the data:
⁃ Each user may see a different view of the database, which describes only the data of interest to
that user.
 Sharing of data and multiuser transaction processing:
⁃
allowing a set of concurrent users to retrieve and to update the database.
⁃ Concurrency control within the DBMS guarantees that each transaction is correctly executed or
completely aborted is a major part of database applications.
⁃ Concurrency control within the DBMS guarantees that each transaction is correctly executed
or aborted.
70
Characteristics of the Database Approach…
 Sharing of data and multiuser transaction processing:
⁃ allowing a set of concurrent users to retrieve and to update the database.
⁃ Concurrency control within the DBMS guarantees that each transaction is
correctly executed or completely aborted is a major part of database
applications.
⁃ Concurrency control within the DBMS guarantees that each transaction is
correctly executed or aborted
⁃ Recovery subsystem ensures each completed transaction has its effect
permanently recorded in the database
⁃ OLTP (Online Transaction Processing) is a major part of database
applications.
⁃ This allows hundreds of concurrent transactions to execute per second.
71
What is a Database Management System (DBMS) ?
 A Database Management System (DBMS) is a software package/ system
designed to enable users to define, create, and maintain the database
and provides controlled access to large collections of database.
⁃ Each DBMS should have facilities to define the database, manipulate
the content of the database and control the database.
⁃ These facilities will help the designer, the user as well as the database
administrator to discharge their responsibility in designing, using and
managing the database.
 A DBMS is software package used to design, manage, and maintain
databases.
72
What is a Database Management System (DBMS) ?

It is a software that enables users to define, create,
maintain and control access to the database.
•
used for providing Efficient, Convenient and Safe, Multi- User
(many people/programs accessing same database, or even same
data, simultaneously) storage of and access to Massive amounts
of Persistent (data outlives programs that operate on it) data.
Popular databases include:
Oracle, MS-Access, MS SQL Server, MySQL, DB2 (IBM),
Ingres, Postgre SQL, FoxPro, SQL Server.
DBMS is the tool for creating and managing the large amounts of
data efficiently and allowing it to persist for a long periods of time.
73
Database Management System…
 Hence DBMS is a general-purpose software that facilities the
processes of defining, constructing, manipulating, and sharing
database.
 Activities of the DBMS:
• Defining: involves specifying data types, structure and
constraints.
• Constructing: is the process of storing the data into a
storage media.
• Manipulating: is retrieving and updating data from and
into the storage.
• Sharing: allows multiple users to access data.
74
Database Management System (DBMS)
 A DBMS also provides a systematic method for creating, updating, storing
and retrieving data in a database.
 It also provides the service of controlling data access, enforcing data
integrity, managing concurrency control, and recovery.
 Having this in mind, a full scale DBMS should at least have the following
services to provide to the user.
• Data storage, retrieval and update in the database
• A user accessible catalogue
• Transaction support service: All or None transaction, which minimize
data inconsistency.
• Concurrency Control Services: access and update on the database by
different users simultaneously should be implemented correctly.
75
Database Management System (DBMS)…
• Recovery Services: a mechanism for recovering the database after a failure must be
available.
• Authorization Services (Security): must support the implementation of access and
authorization service to database administrator and users.
• Support for Data Communication: should provide the facility to integrate with data
transfer software or data communication managers.
• Integrity Services: rules about data and the change that took place on the data,
correctness and consistency of stored data, and quality of data based on business
constraints.
• Services to promote data independency: between the data and the application
• Utility services: sets of utility service facilities like
– Importing data
– Statistical analysis support
– Index reorganization
– Garbage collection
76
Functions of a DBMS
Generally, the Functions of a DBMS includes:
⁃ Data Storage, Retrieval, and Update.
⁃ A User-Accessible Catalogue.
⁃ Transaction Support.
⁃ Concurrency Control Services.
⁃ Recovery Services.
⁃ Authorization Services.
⁃ Support for Data Communication.
⁃ Integrity Services.
⁃ Services to Promote Data Independence.
⁃ Utility Services.
77
Advantages and Disadvantages of DBMSs
Advantages of DBMSs:
⁃ Control of data redundancy
⁃ Data consistency
⁃ Sharing of data
⁃ Improved data integrity
⁃ Improved maintenance through data independence.
Disadvantages of DBMSs:
⁃ Complexity
⁃ Cost of DBMS
⁃ Cost of conversion
⁃ Performance
⁃ Higher impact of a failure
78
What the DBMS does?
• Additionally, DBMS can also provides users with the following
facilities:
• Data definition language (DDL):
»
a language used to define each data element
• Data manipulation language (DML)
» language used by end-users and programmers to
store, retrieve, and access the data. E.g. SQL
• Data dictionary: a tool used to store and organize information
about the data. This describes the database itself
•Data control language (DCL)
• Thus, DBMS provides: Persistence, Security, Data independence
Integrity and Concurrency
79
Database Management system(DBMS) Environment
Note: Database System (DBS) contains: The Database + The DBMS +
Application Programs (what users interact with).
80
Components of DBMS Environment

A database system consists of
•

Data (the database)
DBAs, application programmers, and
⁃ Used by the organization and a description of
end-users.
this data called the schema.
•
Software
⁃ DBMS, operating system, network software
People Includes database designers,
•
We focus mainly on the software
•
Database systems allow users to
(if necessary) and also the application
programs.
•
Hardware
⁃ Can range from a PC to a network of
computers.
• Procedures
⁃ Instructions and rules that should be applied
to the design and use of the database and
⁃ Store
⁃ Update
⁃ Retrieve
⁃ Organise
⁃ Protect their data.
DBMS.
81
Components of DBMS Environment...
 Taking a DBMS as a system, one can describe it with respect to its environment
or other systems interacting with the DBMS.
 To design and use a database, there should be the interaction or integration
of hardware, software, data, procedure and people.
 Generally, the DBMS environment has five components:
1)Hardware
⁃ Can range from a PC to a network of computers.
⁃ are components that one can touch and feel.
⁃ These components are comprised of various types of personal
computers, mainframe or any server computers to be used in multiuser system, network infrastructure, and other peripherals required in
the system.
82
Components of DBMS Environment...
2)Software
⁃ DBMS, operating system, network software (if necessary)
and also the application programs.
⁃ are collection of commands and programs used to
manipulate the hardware to perform a function.
⁃ These
include
application
components
programs,
like
the
operating
DBMS
software,
systems,
network
software, language software and other relevant software.
83
Components of DBMS Environment...
3)Data
⁃ Used by the organization and a description of this data called
the schema.
⁃ since the goal of any database system is to have better control
of the data and making data useful, data is the most important
component to the user of the database.
• There are two categories of data in any database system:
1) Operational data: is the data actually stored in the system to be
used by the user.
2) Metadata: is the data that is used to store information about the
database itself.
• The structure of the data in the database is called the schema,
which is composed of the Entities, Properties of entities, and
relationship between entities.
84
Components of DBMS Environment...
4)Procedures:
⁃ Instructions and rules that should be applied to the design and use of the database
and DBMS.
⁃ It is the rules and regulations on how to design and use a database.
⁃ It includes procedures like how to log on to the DBMS, how to use facilities,
how to start and stop transaction, how to make backup, how to treat
hardware and software failure, how to change the structure of the database.
5)People (user):
⁃ this component is composed of the people in the organization that are responsible or
play a role in designing, implementing, managing, administering and using the
resources in the database.
⁃ These users can be classified as “Actors on the Scene” and “Workers behind the
Scene”.
85
Advantages of a DBMS
 Using a DBMS to manage data has many advantages:
1) Data independence:
o Application programs should be as independent as possible from
details of data representation and storage.
o The DBMS can provide an abstract view of the data to insulate
application code from such details.
2) Efficient Data access:
o A DBMS utilizes a variety of sophisticated techniques to store
and retrieve data efficiently.
o This feature is especially important if the data is stored on
external storage devices.
86
Advantages of a DBMS…
3)Data Integrity and Security:
o If data is always accessed through the DBMS, the DBMS can enforce integrity
constraints on the data.
•
E.g., before inserting salary information for an employee, the DBMS can
check that the organization budget is not exceeded.
o Also, the DBMS can enforce access controls that govern what data is visible to
different classes of users.
4)Data administration:
o When several users share the data, centralizing the administration of data can offer
significant improvements.
o Experienced professionals who understand the nature of the data being
managed, and how different groups of users use it, can be responsible for
organizing the data representation to minimize redundancy and for fine
tuning the storage of the data to make retrieval efficient.
87
Advantages of a DBMS…
5). Concurrent access and crash recovery:
o A DBMS schedules concurrent accesses to the data in such a manner that users can
think of the data as being accessed by only one user at a time.
o Further, the DBMS also protects users from the effects of system failures.
6)Reduced application development time:
o Clearly, the DBMS supports many important functions that are common to many
applications accessing data stored in the DBMS.
o This, in conjunction with the high-level interface to the data, facilitates quick
development of applications.
•
Such applications are also likely to be more robust than applications
developed from scratch because many important tasks are handled by the
DBMS instead of being implemented by the application.
o DBMS includes several important functions that are common to many applications
accessing data in the DBMS.
88
When not to use a DBMS
•
Main inhibitors (costs) of using a DBMS are:
⁃ High initial investment and possible need for additional hardware.
⁃ Overhead for providing generality, security, concurrency control, recovery, and
integrity functions.
•
When a DBMS may be unnecessary/አላስፈላጊ:
⁃ If the database and applications are simple, well defined, and not expected to
change.
⁃ If there are stringent(ጥብቅ) real-time requirements that may not be met because
of DBMS overhead.
⁃ If access to data by multiple users is not required.
•
When no DBMS may suffice:
⁃ If the database system is not able to handle the complexity of data because of
modeling limitations
⁃ If the database users need special operations not supported by the DBMS.
89
Database Users
• Users may be divided into:
– Those who actually use and
– Those who design and
develop the DBMS
control the database content,
software and related
and
tools, and
– those who design, develop
– the computer systems
and maintain database
operators (called
applications (called “Actors
“Workers Behind the
on the Scene”), and
Scene”).
90
Database Users…
 Actors on the Scene:
• Data Administrator
 Workers behind the Scene:
•
DBMS designers and implementers: who design and
implement different DBMS software.
• Database
•
Administrator
Tool Developers: experts who develop software
packages that facilitates database system designing
and use.
• Database Designer
 Prototype, simulation, code generator developers could
be an example.
• End Users
 Independent
software
vendors
could
also
be
categorized in this group.
•
Operators and Maintenance Personnel: system
administrators who are responsible for actually
running and maintaining the hardware and software
of the database system and the information technology
(IT ) facilities.
91
Database Users…
• End users
– Use the database system to
achieve some goal
• Application developers
– Write software to allow end
users to interface with the
database system
• Database Administrator
(DBA)
– Designs & manages the
database system
• Database systems programmer
– Writes the database
software itself
 For a small personal database, one person typically defines, constructs,
and manipulates the database, and there is no sharing.
 However, in large organizations, many people are involved in the design,
use, and maintenance of a large database with hundreds of users.
92
Users of Database Systems
1. Database Administrators (DBA):
• Database Administrator is a person that is responsible for all technical
operations or details of the database system. The user that controls the
enterprises data resource.
• In any organization where many people use the same resources, there is a need for a
chief administrator to oversee and manage these resources.
• In a database environment, the primary resource is the database itself, and the
secondary resource is the DBMS and related software.
• Administering these resources is the responsibility of the database administrator
(DBA).
• The DBA is responsible for authorizing access to the database, coordinating and
monitoring the use of the database, and acquiring software and hardware resources
as needed.
• The DBA is accountable for problems such as security breaches and poor system
response time.
93
Users of Database Systems..
Database Administrators (DBA)…
• In large organizations, the DBA is assisted by a staff that carries
out these functions.
• Responsible to oversee, control and manage the database resources
(the database itself, the DBMS and other related software)
• Responsible for determining and acquiring hardware and
software resources
• Accountable for problems like poor security, poor performance
of the system
• Involves in all steps of database development
94
Users of Database Systems..
• We can have further classifications of this role in big organizations
having huge amount of data and user requirement.
a) Data Administrator (DA):
• is responsible on management of data resources.
• is involved in database planning, analysis, design (conceptual and
logical phase of design), policies and procedures.
b) Database Administrator (DBA):
• is a more technical role.
• It is responsible for the physical realization of the database.
• DBA is participates in physical design, implementation, security and
integrity control of the database.
95
Users of Database Systems…
The functions of the DBA include the following:
 Defining the conceptual schema:
• Will directly participate or help on the process of
identifying the content of the database, i.e., what
information is to be held in the database and create the
corresponding conceptual schema using the conceptual DDL.
 Defining the internal schema:
• The DBA must also decide how the data is to be
represented in the stored database and then create the
corresponding storage structure definition (the internal
schema) using the internal DDL (including associated
mapping between the internal and conceptual schema).
96
Users of Database Systems…
 Liaising with users:
• By communicating with users the DBA will ensure that the data
they require is available, and to write (or help users write) the
necessary external schemas using the applicable external DDL.
• Other functions include consulting on application design,
providing technical education, assisting with problem
determination and resolution, and similar system related
professional services.
 Defining backup and recovery procedures:
• In the event of damage to any portion of a database, caused by
human error or failure in the hardware or operating system, it is
essential to be able to repair the data concerned with the minimum
of delay and with as little effect as possible on the rest of the
system.
• The DBA should define and implement appropriate backup and
recovery scheme.
97
Users of Database Systems…
 Defining security and integrity rules:
• Since security and integrity rules are part of the conceptual
schema, the conceptual DDL should include facilities for
specifying such rules.
 Monitoring
performance
and
responding
to
changing
requirements:
• Periodic performance analysis should be done by the DBA
and based on the results obtained propose for improved
systems and or do the modifications on the existing data
definitions
98
Users of Database Systems…
2. Database Designer (DBD):
• Database designers are responsible for identifying the data to be stored
in the database and for choosing appropriate structures (data model) to
represent and store this data.
• These tasks are mostly undertaken before the database is actually
implemented and populated with data.
• It is the responsibility of database designers to communicate with
all prospective database users in order to understand their requirements
and to create a design that meets these requirements.
• Responsible to define the content, the structure, the constraints, and
functions or transactions against the database.
• They must communicate with the end-users and understand their needs.
99
Users of Database Systems…
• Database Designer (DBD)…
• In many cases, the designers are on the staff of the DBA and may be assigned
other staff responsibilities after the database design is completed.
• Database designers typically interact with each potential group of users and
develop views of the database that meet the data and processing requirements of
these groups.
• Each view is then analysed and integrated with the views of other user groups.
• The final database design must be capable of supporting the requirements of all
user groups.
• Should understand the user requirement and should choose how the user views
the database.
• Involve on the design phase before the implementation of the database system.
100
Users of Database Systems…
• We have two distinctions of database designers, one involving in the
logical and conceptual design and another involving in physical design.
1) Logical and Conceptual DBD:
₋ Identifies data (entity, attributes and relationship) relevant to the
organization.
₋ Identifies constraints on each data
₋ Understand data and business rules in the organization.
₋ Finally, choose appropriate data model which used to represent
those data.
2) Physical DBD:
₋ Take logical design specification as input and decide how it should
be physically realized.
₋ Map the logical data model on the specified DBMS with respect to
tables and integrity constraints. (DBMS dependent designing)
₋ Select specific storage structure and access path to the database
101
₋ Design security measures required on the database
Users of Database Systems…
3. End Users:
– End users are the people whose jobs require access to
the database for querying, updating, and generating
reports; the database primarily exists for their use.
– These are those people who are engaged on
processing different types of operations on the
database system.
– Users are workers, whose job requires accessing the
database frequently for various purpose.
102
Users of Database Systems…
End Users:
• There are several categories of end users:
1. Casual Users:
₋ Users who access the database occasionally/አልፎ አልፎ.
₋ Need different information from the database each time.
₋ Use sophisticated(የተራቀቀ) database queries to satisfy
their needs.
₋ They are typically middle or high-level managers or other
occasional browsers.
103
Users of Database Systems…
104
Users of Database Systems…
2. Naïve Users:
₋ Unaware of the DBMS
₋ Only access the database based on their access level and demand
₋ Use standard and pre-specified types of queries.
 Naive or parametric end users make up a sizable portion of database
end users.
– Their main job function revolves around constantly querying and
updating the database, using standard types of queries and updates
called canned transactions that have been carefully programmed
and tested.
105
Users of Database Systems…
Naïve Users:
• The tasks that such users perform are varied:
– Bank tellers check account balances and post withdrawals and deposits.
– Reservation agents for airlines, hotels, and car rental companies check
availability for a given request and make reservations.
– Employees at receiving stations for shipping companies enter package
identifications via bar codes and descriptive information through buttons
to update a central database of received and in-transit packages.
3. Sophisticated Users
₋ Are users familiar with the structure of the Database and facilities of the
DBMS
₋ Have complex requirements
₋ Have higher level queries
106
Users of Database Systems…
•
Sophisticated end users include most of the time engineers, scientists, business
analysts, and others who thoroughly familiarize themselves with the facilities of the
DBMS in order to implement their own applications to meet their complex
requirements.
•
Standalone users maintain personal databases by using ready-made program
packages that provide easy-to-use menu-based or graphics-based interfaces.
•
An example is the user of a tax package that stores a variety of personal financial data
for tax purposes.
– Mostly maintain personal databases using ready-to-use packaged
applications.
– An example is a tax program user that creates its own internal database.
– Another example is maintaining an address book
 Generally, End users are those that interact with the system from online workstations or
terminals that use an application program developed by application programmers or
those that query the system through an interface provided by the DBMS.
107
Users of Database Systems…
 Thus:
⁃ A typical DBMS provides multiple facilities to access a database.
⁃ Naive end users need to learn very little about the facilities provided by the
DBMS; they simply have to understand the user interfaces of the standard
transactions designed and implemented for their use.
⁃ Casual users learn only a few facilities that they may use repeatedly.
⁃ Sophisticated users try to learn most of the DBMS facilities in order
to
achieve their complex requirements.
⁃ Standalone users typically become very proficient in using a specific software
package.
108
Users of Database Systems…
4. Application Programmer and Systems Analyst
• System analyst determines the user requirement and how the user wants to
view the database.
• The application programmer implements these specifications as programs;
code, test, debug, document and maintain the application program.
– Determines the interface on how to retrieve, insert, update and delete
data in the database.
– The application could use any high level programming language
according to the availability, the facility and the required service.
• System analysts determine the requirements of end users, especially naive
and parametric end users, and develop specifications for standard canned
transactions that meet these requirements.
109
Users of Database Systems…
Application Programmer and Systems Analyst…
– Application programmers implement these specifications as
programs; then they test, debug, document, and maintain these
canned transactions.
– Such analysts and programmers commonly referred to as
software developers or software engineers should be familiar
with the full range of capabilities provided by the DBMS to
accomplish their tasks.
– Application programmers who are responsible for writing
application programs that use the database using some
programming language such as COBOL, Pascal, or a
programming language built-in to the DBMS.
110
Users of Database Systems…
⁃ In addition to those who design, use, and administer a database, others are
associated with the design, development, and operation of the DBMS
software and system environment.
⁃ These persons are typically not interested in the database content itself.
⁃ We call them the workers behind the scene,(DBMS designers and
implementers: who design and implement different DBMS software. ) and
they include the following categories:
1. DBMS system designers and implementers:
•
design and implement the DBMS modules and interfaces as a software
package.
• A DBMS is a very complex software system that consists of many
components, or modules, including modules for implementing the catalogue,
query language processing, interface processing, accessing and buffering data,
controlling concurrency, and handling data recovery and security.
• The DBMS must interface with other system software such as the operating
system and compilers for various programming languages.
111
Users of Database Systems…
2. Tool developers:
– experts who develop software packages that facilitates database system
designing and use.
– Prototype, simulation, code generator developers could be an example.
Independent software vendors could also be categorized in this group.
– design and implement tools the software packages that
facilitate database modelling and design, database system design, and
improved performance.
⁃ Tools are optional packages that are often purchased separately. They
include packages for database design, performance monitoring, natural
language or graphical interfaces, prototyping, simulation, and test data
generation.
⁃ In many cases, independent software vendors develop and market these
tools.
112
Users of Database Systems…
3. Operators and Maintenance Personnel:
⁃ system administrators who are responsible for actually running and
maintaining the hardware and software of the database system and
the information technology facilities.
⁃ Operators and maintenance personnel (system administration
personnel are responsible for the actual running and maintenance of
the hardware and software environment for the database system.
⁃ Although these categories of workers behind the scene are
instrumental in making the database system available to end users,
they typically do not use the database contents for their own
purposes.
113
Types of SQL Languages
1. Data Definition Language (DDL):
– define a database, including creating, altering, and dropping tables and
establishing constraints
– DDL is a language which describes each data element required by the
organization.
– The main purpose of this language is to create database and table, insert
data inside the database, alter the schema of data inside the database
and drop the database include the all data that found inside that
database.
– DDL has their own commands to achieve the above functions.
– This DDL commands are: create, insert, alter and drop commands.
114
Types of SQL Languages…
Data Definition Language (DDL)…
– The above DDL commands are used by database designer and
database administrator.
– Commands for setting up schema or the intension of database
– These commands are used to setup a database, create, delete and
alter table with the facility of handling constraints.
– Allows DBA or user to describe and name entitles, attributes and
relationships required for the application.
– Specification notation for defining the database schema
115
Types of SQL Languages…
2. Data Manipulation Language (DML):
– maintain and query a database
– DML is a core language which is used to update, retrieve and access the
data in the database
– Like DDL, DML has their own commands to achieve the above functions.
» These commands are: select, update and delete commands.
– The above commands are used by end users and database administrator.
– Is a core command used by end-users and programmers to store, delete,
and update the data in the database.
– Provides basic data manipulation operations on data held in the database.
– Language for manipulating the data organized by the appropriate data
model
116
Types of SQL Languages…
 Data Manipulation Language can be categorized in to two:
1) Procedural Data Manipulation Languages: allows the user to tell the
system what data is needed and exactly how to retrieve the data;
2) Non-Procedural Manipulation Languages: allows the user to state what
data is needed rather than how it is to be retrieved.
Example: Data Manipulation Language
117
Types of SQL Languages…
3. Data Query Language (DQL):
• Language for accessing or retrieving the data organized by the
appropriate data model.
• Since the required data or Query by the user will be extracted
using this type of language, it is also called "Query Language"
– Procedural DQL: user specifies what data is required and how to get the
data.
– Non-Procedural DQL: user specifies what data is required but not how it is
to be retrieved.
118
Types of SQL Languages…
4. Data Control Language:
– control a database, including administering privileges and committing
data
– Database is a shared resource that demands control of data access and
usage.
– Data Control Languages are languages that will helps to control the overall
operation of the database.
– Like DDL and DML, DCL has their own commands to control the overall
operation of the DB.
– These commands are: grant and revoke commands which
are used by database administrator (DBA).
– The database administrator should have the facility to control the overall
operation of the system.
119
Types of SQL Languages…
Data Control Language (DCL):
– The commands include grant or revoke privileges to access the
database or particular object within the database and to
store or remove database transactions.
– This DBA has the power to give privileges to different users to
access the database at different level or particular object
within the database and to store or remove database
transactions by using the above commands.
120
Types of SQL Languages…
 DDL, DML, DCL, and the database development process:
121
Data Dictionary - Metadata

The dictionary or catalogue
stores information about the

– Descriptions of database
database itself
objects (tables, users, rules,
This is data about data or
views, indexes,…)
‘metadata’

• The dictionary holds
Almost every aspect of the
DBMS uses the dictionary
– Information about who is
using which data (locks)
– Schemas and mappings
Data Dictionary:
• Due to the fact that a database is a self-describing system,
this tool, Data Dictionary, is used to store and organize
information about the data stored in the database.
122
Database Development Life Cycle
• As it is one component in most information system development
tasks, there are several steps in designing a database system.
• The major steps in database design are;
1) Planning:
₋
identifying information gap in an organization and
propose a database solution to solve the problem.
2) Analysis:
₋
₋
concentrates more on fact finding about the problem or the
opportunity.
Feasibility analysis, requirement determination and structuring, and
selection of best design method are also performed at this phase.
123
Database Development Life Cycle
3). Design: The activity of specifying the schema of a database in a given data
model . Here more emphasis is given to the design phases of the system
development life cycle.
This phase is further divided into three sub-phases.
a) Conceptual Design: concise description of the data, data type,
relationship between data and constraints on the data.
• There is no implementation or physical detail consideration.
• Used to elicit and structure all information requirements
b) Logical Design: a higher level conceptual abstraction with selected specific
data model to implement the data structure.
• It is particular DBMS independent and with no other physical
considerations.
124
Database Development Life Cycle
c). Physical Design: physical implementation of the upper level
design of the database with respect to internal storage and file
structure of the database for the selected DBMS.
• To develop all technology and organizational specification.
4). Implementation:
– the deployment and testing of the designed database for use.
5). Operation and Support:
– administering and maintaining the operation of the database
system and providing support to users.
125
Database Development Life Cycle
126
Thank You!
127