Basic Concepts

Course Code: CSC 2108 Course Title: Introduction To Database

Department of Computer Science

Faculty of Science and Technology

Lecture No: 03 Week No: 02 Semester: spring 22-23

Lecturer: SIFAT RAHMAN AHONA
Lecture Outline

 Database Management System (DBMS)

 Application of Database
 Drawbacks of File System
 View of Data
 Level of Abstraction
 Schema and Instance
 Data Independence
 Data Models
 Database Languages: DML , DDL, SQL
 Database Design
 Storage Management
 Database Users
 Database Administrators
Database Management System(DBMS)

Contains information about a particular enterprise

 Collection of interrelated data
 Set of programs to access the data
 An environment that is both convenient and efficient to
use
Application of Database

• Banking: all transactions

• Airlines: reservations, schedules
• Universities: registration, grades
• Sales: customers, products, purchases
• Manufacturing: production, inventory, orders, supply chain
• Human resources: employee records, salaries, tax
deductions
Drawbacks of Using File System for Data
Storage

• Data Redundancy and Inconsistency

• Difficulty in Accessing Data
• Data Isolation
• Integrity Problems
• Atomicity of updates
• Concurrent access by multiple users
• Security problems
 6

Drawbacks of Using File System for Data

Storage

• Data Redundancy and • Data Isolation

Inconsistency -> Multiple files and formats
->Multiple file formats -> Difficult if we write different
->duplication of information parts in different programming
in different files language.

• Difficulty in Accessing • Integrity Problems

Data ->Integrity
constraints/rule/condition
->Need to write a new (e.g. account balance > 0)
program to carry out become “buried” in program
each new task code rather than being stated
explicitly
->Hard to add new constraints or
change existing ones
 7

Drawbacks of Using File Systems for Data

Storage

• Atomicity of • Concurrent access by • Security problems

updates multiple users ->Hard to provide
->Failures may leave ->Concurrent accessed user access to
database in an needed for some, but not all,
inconsistent state performance data
with partial ->Uncontrolled
updates carried concurrent accesses
out can lead to
Example: Transfer inconsistencies
of funds from one Example: Two people
account to reading a balance
another should and updating it at
either complete or the same time
not happen at all
Database systems offer solutions to all of the problems that have been
mentioned
View of Data

•Database system is a collection of interrelated data and a set of

programs to access and modify these data
•Major purpose of a database system is to provide users with an
abstract view of the data
• The system hides certain details of how data are stored and
maintained
Levels of Abstraction

•Physical Level
•Logical Level
•View Level
 10

Levels of Abstraction
Since many database-system users are
not computer trained, developers
hide the complexity from users  Logical level:
through several levels of abstraction,  Next higher level
to simplify users interaction with the  Describes what data are stored
system.
in database, and the
 relationships among the data
Physical level:
 Lowest level
 describes how a record (e.g.,
customer) is stored  View level:
 Complex low level data structures  Application programs hide
details of data types
 Views can also hide information
(such as an employee’s salary)
for security purposes
Schema and Instance

Schema – the logical structure of the database

• Example: The database consists of information about a set of customers and
accounts and the relationship between them
• Analogous to type information of a variable in a program
• Physical schema: database design at the physical level
• Logical schema: database design at the logical level

Instance – the actual content of the database at a particular point

in time
• Analogous to the value of a variable
Data Independence

Physical Data Independence – the ability to modify the physical

schema without changing the logical schema
• Applications depend on the logical schema
• In general, the interfaces between the various levels and components should be well
defined so that changes in some parts do not seriously influence others

Logical Data Independence - the ability to modify the logical

schema without causing application programs to be rewritten.
• Required when the logical structure has been altered
Data Models

A collection of tools for describing

 Data
 Data relationships
 Data semantics (Logical and Lexical)
 Data constraints
 Data Models
Relational Model , ER Model and Other Data Models

•The relational model uses a collection of tables to represent both

data and the relationships among those data.
•The E-R data model is based on a perception of a real world that
consists of a collection of basic objects, called entities and of
relationships among these objects.
•Object-based data models (Object-oriented and Object-
relational)
•Semi-structured data model (XML)
•Otherolder models:
Network model
 Hierarchical model
Database Language
DML

Stands for Data Manipulation Language

DML OPERATIONS: INSERT, UPDATE, DELETE, MERGE
Language for accessing and manipulating the data organized by the
appropriate data model
 DML also known as query language

Type of access are:

 Retrieval of information stored in the database
 Inserting of new information into the database
 Deletion of information from the database
 Modification of information stored in the database
Database Language
DDL

Stands for Data Definition Language (DDL)

Data dictionary contains metadata (i.e. data about data)
DDL OPERATIONS: CREATE, ALTER, DROP, RENAME,
TRUNCATE
Database Language
SQL

Widely used non-procedural language

SQL is used to communicate with a database
Database Design
Logical and Physical Design

The process of designing the general structure of the database:

 Logical Design – Deciding on the database schema. Database design

requires that we find a “good” collection of relation schemas.
 Business decision – What attributes should we record in the
database?
 Computer Science decision – What relation schemas should
we have and how should the attributes be distributed among
the various relation schemas?

 Physical Design – Deciding on the physical layout of the database

Storage Manager
Components

 Storage manager is a program module that provides the interface between

the low-level data stored in the database and the application programs and
queries submitted to the system.

 The storage manager is responsible to the following tasks:

 Interaction with the file manager
 Efficient storing, retrieving and updating of data

 Components of Storage Manager

 Authorization and integrity manager
 Transaction manager
 File manager
 Buffer manager
 20

Storage Manager
 Authorization and Integrity Manager: Checks the authority of users to access data.

 Transaction manager: Ensure that the database in a consistent state despite system
failures, and that concurrent transaction execution proceed without conflicting.

 File manager : Manage allocation of space on disk storage and the data structures
used to represent information stored on disk.

 Buffer manager : Responsible for fetching data from disk storage into main memory
and decide what data to cache in main memory. The data buffer manager is a critical
part of the database system, since it enables the database handle data sizes that are
much larger than the size of main memory.
 Storage Manager
Data Structure

The storage manager implements several data structure as part

of the physical system implementation

•Data files: Store the database itself.

•Data dictionary : stores metadata about the structure of the
database, in particular the schema of the database.

•Indices: Provide first access to the data items. Like index of the
textbook.
Database Users
Types

Users are differentiated by the way they expect to interact with

the system
• Application programmers
• Sophisticated users
• Specialized users
• Naive users
 23

Database Users

Users are differentiated by the way they  Specialized users

expect to interact with the system  One type of sophisticated user
 Write specialized database applications
 Application programmers
that do not fit into the traditional data
 Computer professionals who write
processing framework (expert system,
application programs knowledge base, graphics data, audio
 Can use RAD tools for constructing forms data)
and reports with minimal programming
efforts.  Naive users
 Invoke one of the permanent application
 Sophisticated users
programs that have been written
 Interact with the system without writing previously
programs  Read reports
 Form requests in a database query  Examples, people accessing database
language over the web, bank tellers,
 Submit query to the query processor
 Analyst
Database Administrator
Duties

 Coordinates all the activities of the database system; the database

administrator has a good understanding of the enterprise’s information
resources and needs.
 Database administrator's duties include:
 Schema definition : The DBA create the original database schema by
executing a set of data definition statements in the DDL
 Storage structure and access method definition
 Schema and physical organization modification
 Granting user authority to access the database
 Specifying integrity constraints
 Acting as liaison with users
 Monitoring performance and responding to changes in requirements
Books

1. Modern Database Management (Sixth Edition) by Fred R. McFadden, Jeffrey A.

Hoffer, Mary B. Prescott
2. Database System Concepts (Fifth Edition) by Henry F. Korth, S. Sudarshan, A.
Silberschatz
3. Oracle-database-10g-sql-fundamentals-1-student-guide-volume-1
4. SQL and Relational Theory: How to Write Accurate SQL Code by C.J. Date
5. Database Systems: A Practical Approach to Design, Implementation and
Management (4th Edition) by Thomas M. Connolly, Carolyn E. Begg
6. Fundamentals of Database Systems, 5th Edition by RamezElmasri, Shamkant B.
Navathe
7. Database Design and Relational Theory: Normal Forms and All That Jazz by C. J. Date
8. An Introduction to Database Systems 8th Edition, by C.J. Date
References

1. https://www.db-book.com/db6/slide-dir/index.html
2. https://docs.oracle.com/en/database/oracle/oracle-database/20/sqlrf/SQL-Sta
ndards.html#GUID-BCCCFF75-D2A4-43AD-8CAF-C3C97D92AC63
3. https://www.slideshare.net/HaaMeemMohiyuddin1/data-knowledge-and-infor
mation
4. https://www.slideshare.net/tabinhasan/from-data-to-wisdom
5. https://www.slideshare.net/thinnaphat.bo/