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Database Management System
Lecture 2
Introduction to Database management
Learning Outcomes
• Understanding the definition of a Database
management System (DBMS)
• Grasping an outline of DBMS architectures
• Understanding DBMS’s main functionalities
• Get introduced to a number of commercial
DBMSs which are widely used.
List of Topic
• DBMS definition
• DBMS functionalities
• DBMS Examples
Terminology
1 Database
2 DBMS
3 Table
A collection of related information
stored in a structured format
Database management system. A
program or environment which hosts
one database or more and provide
support for managing information in
such databases
A single store of related information.
A table consists of records, and each
record is made up of a number of
fields
Terminology
4 SQL
It stands for Structured Query
Language, the standard format for
commands that most database
software understands
5 RDBMS Relational DBMS
DBMS definition
• DBMS is a collection of software for creating,
managing and effectively searching a database.
DBMS Role Illustration
DBMS definition (con.)
• In addition a DBMS is responsible for
managing application requests to a database
DBMS Three-Schema Architecture
DBMS Three-Schema Architecture
(con.)
• The architecture ensures:
•
•
•
•
the independence of logical and physical data
allowing the manipulation of data
ensure data integrity
optimize data access.
DBMS Three-Schema Architecture
(con.)
1- External layer or External Schema
• It covers all the possibilities of access to data by
different users.
• Access of different user groups can be done via
different applications.
DBMS Three-Schema Architecture
(con.)
2- Each external schema describes
• the part of the database that a particular
user is
interested in
• hides the rest of the database from user.
DBMS Three-Schema Architecture
(con.)
2-
Logical Layer or Logical Schema
• It is the general view of the data independent of
individual applications and how data is stored.
• It hides the details of physical storage
structures and concentrates on describing
entities, data types, relationships, user
operations, and constraints.
DBMS Three-Schema Architecture
(con.)
3-
Internal layer or Internal Schema
• Describes the physical storage structure of the
database.
• The internal schema describes the complete details of
data storage and access paths for the database.
DBMS Functionalities
1-Support the concepts defined in the data model
in order to represent data properties.
• It usually includes the definition of
specific types and the definition of
consistency rules.
DBMS Functionalities (con.)
2-
Make transparent data sharing between
different users.
• This means that multiple users should be
able to use the database concurrently and
transparently
DBMS Functionalities (con.)
3-
Ensure confidentiality of data
• to specify who has the right to access or modify
all or part of a database.
• first requires a user identification
• second requires a specification of privileges (add,
delete, update).
DBMS Functionalities (con.)
4-Ensure compliance with the consistency rules
defined on the data
• after each modification on the database, all rules
of consistency must be checked on all data
DBMS Functionalities (con.)
5-Being resistant to failure.
• this is to protect data against hardware failure
or software whether intentional or accidental.
DBMS Functionalities (con.)
6- Possess a high storage capacity
• Thus enabling data management up to several
billion bytes
• The storage units are moved from the megabyte
(106) to gigabyte (109), then to terabyte (1012),
peta-byte (1016), and we start talking about
exabytes (1018) even zettabyte (1021).
DBMS Functionalities (con.)
7- To answer queries with a level of acceptable
performance
• A query requires searching data in a database
based on some conditions
• Computer power is not the only possible
answer to the problems of performance
• Query optimization can be very effective to
ensure
Database Examples
• Is widely used due to its ease of integration
with the Apache/PHP and its good response
time.
• MySQL supports only part of the standard
SQL-92.
Database Examples (con.)
1. MySQL:
• It does not support native transactions, subqueries,
triggers and stored procedures.
• Lacks some features compared to other DBMSs
Database Examples (con.)
2 Oracle
• is a RDBMS which supports remote access to the
database hosted in it.
• It is one of the best performing DBMS with powerful
tools.
• Oracle is a RDBMS-oriented environments with heavy
constraints (availability, integrity, stability, large
volumes of data and high number of users, etc..).
Database Examples (con.)
3 PostgreSQL
• PostgreSQL is usable under Linux.
• Is an excellent choice to manage databases of
medium size.
• It is free.
Database Examples (con.)
4 Borland Interbase
• One of its main strengths is its availability in
an open source version
• A good choice to manage databases for small
and medium size
Database Examples (con.)
5 Microsoft SQL Server
• SQL Server is a good choice for databases of
medium size
Database Examples (con.)
6 Access
• Developed by Microsoft
• Suitable for supporting small databases
(personal).
Summary
In this lesson, the following has been discussed:
• The definition of DBMS and its role.
• The DBMS architecture based on the three-schema
architecture.
• The main features that a robust and reliable DBMS
must have.
• An outline of the most widely used DBMSs.
Exercises
• What are the three layers constituting a DBMS
architecture ?
• Which layer in DBMS architecture interacts
with end users or user applications ?
• List the most important features which must
belong to a DBMS?
• List four widely used DBMSs?
Self-assessment
1
Search the web and find a good reference for
the SQL language. Identify the SQL command that
could be used to:
• Create a table.
• Insert a record in a table.
• Modify a data field in a table record.