Data base chapter 1 | the complete note of database

Database Systems
Introduction Database Management Systems
1
Lecture 1

Today’s agenda
• Database introduction and definition
• DBMS functionalities
• Characteristics of database approach
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Database Management Systems

Database definition
• A shared collection of logically related data,
designed to meet the information needs of
multiple users in an organization.
• The term database is often erroneously referred
to as a synonym for a “database management
system (DBMS)”.
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Basic Definitions
• Database: A collection of related data.
• Data: Known facts 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. For example,
student grades and transcripts at a university.
• Database Management System (DBMS): A
software package/ system to facilitate the
creation and maintenance of a computerized
database.
• Database System: The DBMS software
together with the data itself. Sometimes, the
applications are also included.
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A simplified database system environment
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Typical DBMS Functionality
• Define a database : in terms of data types,
structures and constraints
• Construct or Load the Database on a secondary
storage medium
• Manipulating the database : querying,
generating reports, insertions, deletions and
modifications to its content
• Concurrent Processing and Sharing by a set of
users and programs – yet, keeping all data valid
and consistent
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Typical DBMS Functionality
Other features:
▫ Protection or Security measures to
prevent unauthorized access
▫ “Active” processing to take internal
actions on data
▫ Presentation and Visualization of data
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Example of a Database
(with a Conceptual Data Model)
• Mini-world for the example: Part of a
UNIVERSITY environment.
• Some mini-world entities:
▫ STUDENTs
▫ COURSEs
▫ SECTIONs (of COURSEs)
▫ (academic) DEPARTMENTs
▫ INSTRUCTORs
Note: The above could be expressed in the
ENTITY-RELATIONSHIP data model.
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Example of a Database
(with a Conceptual Data Model)
• Some mini-world relationships:
▫ SECTIONs are of specific COURSEs
▫ STUDENTs take SECTIONs
▫ COURSEs have prerequisite COURSEs
▫ INSTRUCTORs teach SECTIONs
▫ COURSEs are offered by DEPARTMENTs
▫ STUDENTs major in DEPARTMENTs
Note: The above could be expressed in the
ENTITY-RELATIONSHIP data model.
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Example of a database
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Main Characteristics of the Database
Approach
• 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.
• Insulation between programs and data: Called
program-data independence. Allows
changing data storage structures and
operations without having to change the
DBMS access programs.
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An Example of Database Catalog

Storage format for a student record
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Approach
• Data Abstraction: A data model is used
to hide storage details and present the
users with a conceptual view of the
database.
• 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.
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Student transcript and course
prerequisites view
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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.
OLTP (Online Transaction Processing) is a
major part of database applications.
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Summary
• Introduction
• Basic definitions
▫ Database
▫ Data
▫ Mini world
▫ DBMS
▫ Database systems
• An example database
• Functionalities of database systems
• Characteristics of database systems
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Data base chapter 1 | the complete note of database

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