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Transcript
DBMS
Introduction to Database Management System
Module Title?
Data vs. Information
DBMS
 Data
 Raw facts, text, graphics, images, sound and video segments that
have meaning in the user’s environment
 Information
 Data that have been processed in such a way as to increase the
knowledge of the person who uses the data
 Data are raw facts. Information is processed data to
reveal the meaning behind the facts.
Module Title?
Traditional Approach
DBMS
 Systems used files to store information
 Separate systems - Separate files and programs for each
application
 E.g. Payroll files, Personnel files, Accounts files etc.
Module Title?
Example of file system
DBMS
Module Title?
Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
Module Title?
Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
wasteful of space (storage)
Module Title?
Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
wasteful of space (storage)
update inefficiencies
Module Title?
Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
wasteful of space (storage)
update inefficiencies
(when
a teacher moves to a new address, or
changes her name, the teacher's "record" must
be changed each place it is stored)
Module Title?
Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
wasteful of space (storage)
update inefficiencies
(when
a teacher moves to a new address, or
changes her name, the teacher's "record" must
be changed each place it is stored)
data inconsistency (different addresses for the same
teacher in different files)
Module Title?
Some Problems with Traditional File Processing
DBMS
Systems
Redundancy (duplication of data)
wasteful of space (storage)
update inefficiencies
(when
a teacher moves to a new address, or
changes her name, the teacher's "record" must
be changed each place it is stored)
data inconsistency (different addresses for the same
teacher in different files)
Module Title?
LIMITATIONS OF FILE-BASED
 SEPARATION AND ISOLATION
DBMS
 Payroll Office files has the teachers' names and id's and departments
 Principal's Office Files has teacher’s names , the current salary scale
and date this salary scale became effective
 Asst. Principal's Office files has seminar topics for each teacher
 PROGRAM & DATA DEPENDENCE
 The Payroll Department has written some lengthy Pascal programs to
access their files and perform queries and reports.
 The Personnel Department has written some C programs to access
their files and perform queries and reports.
Module Title?
Database Approach
DBMS
 Build a SINGLE pool of interrelated files, rather than SEPARATE
collection of files.
 (This is an INFORMAL description of a database).
Module Title?
DATABASE
DBMS
 A COLLECTION OF SELF-DESCRIBING AND INTEGRATED
,ORGANISED DATA
(Kroenke's Definition of a Database)
Module Title?
DATABASE MANAGEMENT SYSTEM (DBMS)
DBMS
 A collection of Programs that enables you to Store, modify, and
extract (access) information from a database.
 Provides the interface between the user and the data in the
database
 Allocates storage to data and maintains indices so that any
required data can be retrieved.
 Protects data against corruption
 Provides recovery and restart facilities after a hardware or
software failure.
Module Title?
Database System:
DBMS
 The DBMS software together with the data itself. Sometimes,
the applications are also included.
database
Application
DBMS
data
catalog
Module Title?
Database vs. File Systems
DBMS
Module Title?
DATABASE MANAGEMENT SYSTEM (DBMS)
DBMS
 The following are examples of Database Applications:
 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
Module Title?
DATABASE MANAGEMENT SYSTEM (DBMS)
DBMS
Different DBMS Software
•
•
•
•
•
•
•
•
•
Module Title?
ORACLE
ACCESS
SQL SERVER
IBM DB2
Sybase
SAP DB
PostgreSQL
MySQL
MS SQL Server, ...
Advantages of Database Approach
DBMS

Controlling redundancy in data storage and in development and
maintenance efforts.

Sharing of data among multiple users.

Restricting unauthorized access to data.

Greater consistency of data

Enforcing integrity constraints on the database.

Providing backup and recovery services.
 Availability of up-to-date information.
Module Title?
Database System Environment
DBMS
Application Programs/ Queries
DBMS
Software
Software to Process
Queries/ Program
Software to Access
Stored Data
Stored Data
Definition
(Meta-Data)
Module Title?
Stored
Database
Data Models
DBMS
 Data Model is a set of concepts that can be used to describe
the structure of a database
 data types, relationships, and constraints

Data Model Examples:
 Relational - describes database structure as tables
 Network - describes database structure as a network
 Object Oriented - describes database structure as objects
Module Title?
HISTORY OF DATABASE SYSTEMS
DBMS
•
•
•
Module Title?
FIRST GENERATION
_ HIERARCHICAL MODEL
• INFORMATION MANAGEMENT SYSTEM (IMS)
– NETWORK MODEL
• CONFERENCE ON DATA SYSTEM LANGUAGES (CODASYL)
• DATA BASE TASK GROUP (DBTG)
SECOND GENERATION
– RELATIONAL MODEL
• E. F. CODD
• DB2, ORACLE
THIRD GENERATION
– EXTENDED RELATIONAL DATA MODEL OR OBJECT-RELATIONAL DATA
MODEL
– OBJECTED-ORIENTED DATA MODEL
Schema Architecture
DBMS
 Database Schema: The description of a database. It Includes
descriptions of the
database structure and the constraints
that should hold on the database.
Module Title?
The three-schema architecture.
DBMS
Module Title?
The three-schema architecture.
DBMS
 External schema describes part of a database that a particular
user or users are interested in.
 Using the relational model, these are views
 Conceptual schema describes the structure of he whole
database for a community of users.
 Using the relational model, these are tables
 Internal schema describes the physical storage structure of the
database.
 These are not tables, this is the data as stored by the DBMS.
Module Title?
ROLES IN DATABASE ENVIRONMENT (USERS)
DBMS
 DATA ADMINISTRATOR
 Implements the database
 APPLICATION PROGRAMMER
 Interact with the database through high level programming
 END-USER
 Interacts and uses the database
Module Title?
Data Dictionary
DBMS
Module Title?
Database Languages
DBMS

Data Definition Language (DDL)
 Used to define the conceptual and internal schemas

Data Manipulation Language (DML)
 Used to describe operations on the instances of a database
 Procedural DML (how) vs. declarative DML (what)
e.g., Relational Algebra

Module Title?
e.g., SQL
Note, SQL includes a DML and a DDL in one!
Database Languages
DBMS
 DCL Data Control Language. [Grant, Revoke commands
(oracle)]
 TCL [Transaction control Language] [Commit, Rollback,
savepoint commands (oracle)]
Module Title?
DBMS
 Classification of DBMS based on the data model used:
 Relational DBMS
 Network DBMS
 Hierarchical DBMS
 Object-oriented DBMS
 Object-relational DBMS
Module Title?
DBMS
 Classification of DBMS based on the number of users:
 Single-user (typically used with micro- computers)
 Multi-user (most DBMSs).
 Classification of DBMS based on the number of sites:
 Centralized (uses a single computer with one database)
 Distributed (uses multiple computers, multiple databases)
Module Title?