an introduction to database system
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An Introduction to database system. Basic Definitions. Data: Meaningful facts, text, graphics, images, sound, video segments. Database: An organized collection of logically related data. Information: Data processed to be useful in decision making. Metadata: Data that describes data. - PowerPoint PPT PresentationTRANSCRIPT
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Database ManagementCOP4540, SCS, FIU
An Introduction to database system
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Database ManagementCOP4540, SCS, FIU
Basic Definitions
• Data: Meaningful facts, text, graphics, images, sound, video segments.
• Database: An organized collection of logically related data.
• Information: Data processed to be useful in decision making.
• Metadata: Data that describes data.
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Database ManagementCOP4540, SCS, FIU
What is a DataBase system?(DB)
• It is a logically coherent collection of data with inherent meaning.
• It represents a miniworld, and should represent the state of that world accurately.
• It is managed by a database management system (DBMS).
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Database ManagementCOP4540, SCS, FIU
What is a DataBase Management System?(DBMS)
• A (large) piece of software which provides an interface between the user or application program and the stored data.
• A DBMS is developed according to a particular data model.
• Some example DBMSs are:
– IMS, DB2, Oracle, Sybase, Informix, SQL Server, Access, FoxPro, O2.
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Database ManagementCOP4540, SCS, FIU
The functionality of DBMS
• Manages very large amounts of data.
• Supports efficient access to very large amounts of data.
• Supports concurrent access to very large amounts of data.
• Supports secure, atomic access to very large amounts of data.
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Database ManagementCOP4540, SCS, FIU
Several basic concepts
• Data models– A data model is a way of representing (part of)
the world.– The principle current data model are:
• Hierarchical
• Network
• Relational
• Object-oriented
• E-R
• Semantic
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Database ManagementCOP4540, SCS, FIU
Several basic concepts
• Database design– Design goals
• Minimize redundancy in order to eliminate the modification anomalies in database.
• Represent the situation accurately
– Design Stages• Conceptual (product independent)
• Logical (product specific)
• Physical / Implementation (product specific)
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Database ManagementCOP4540, SCS, FIU
Database Development Activities
Enterprise ModelingConceptual Data Modeling
Logical DB Design
Physical DB DesignDB Implementation
DB Maintenance
} The stages focused in COP4540
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Database ManagementCOP4540, SCS, FIU
Conceptual Database Modeling
• Determine user requirements.
• Determine business rules.
• Build conceptual data model– outcome is an entity-relationship diagram or
similar communication tool.
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Database ManagementCOP4540, SCS, FIU
Logical Database Design
• Select logical database model.
• Map Entity-Relationship Diagrams
• Normalize data structures.
• Specify business rules.
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Database ManagementCOP4540, SCS, FIU
Physical Database Design
• Select DBMS
• Select storage devices
• Determine access methods
• Design files and indexes
• Determine database distribution
• Specify update strategies
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Database ManagementCOP4540, SCS, FIU
Several basic concepts
• Schema– Logical structure of the data defined by using
data definition language (DDL).
• Queries– A “query” is a database lingo for a question
about the data.– A “query” is composed by using query
language (QL)
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Database ManagementCOP4540, SCS, FIU
The architecture of database system
Users / Programmers
Application Programs / Queries
Database Management System
1. Software to process queries/programs
2. Software to access stored data
Stored data
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Database ManagementCOP4540, SCS, FIU
Components of the Database Environment
• CASE Tools• Repository• Database Management System (DBMS)• Database• Application Programs• User Interface• Database Administrators (DBA)• System Developers• End Users
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Database ManagementCOP4540, SCS, FIU
Evolution of Database Systems
• Hierarchical and Network (Legacy): Data are modeled as linked records.
• Relational: Data are modeled as related tables.• Object-oriented: Data are organized as linked
objects.– Object-relational: Integration of relational and
object-oriented features.
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Database ManagementCOP4540, SCS, FIU
RDBMS and SQL
• RDBMS is a DBMS on the basis of relational model.
• It is the most popular type of the DBMS.
• The data is organized as tables called relations
• Two famous systems:– System R at IBM & Ingres at UC Berkeley
• SQL (Structured Query Language)– the most important query language based on relational
model.
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Database ManagementCOP4540, SCS, FIU
RDBMS and SQL
accountNo balance type
12345 1000.00 savings
67890 2846.92 checking
Accounts
SELECT balanceFROM AccountsWHERE accountNo = 67890
Result: 2846.92
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Database ManagementCOP4540, SCS, FIU
Disadvantages of File Processing Systems
• Data Dependence
• Data Redundancy (Duplication of data)
• Limited Data Sharing
• Lengthy Development Times
• Excessive Program Maintenance
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Database ManagementCOP4540, SCS, FIU
Advantages of Database Approach
• Program-Data Independence: No need to rewrite programs when data is modified
• Minimal Data Redundancy
• Improved Data Consistency
• Improved Data Sharing
• Increased Application Development Productivity.
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Database ManagementCOP4540, SCS, FIU
Advantages of Database Approach
• Enforcement of Standards
• Improved Data Quality (Constraints)
• Better Data Accessibility/Responsiveness
• Reduced Program Maintenance
• Security, Backup/Recovery, Concurrency
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Database ManagementCOP4540, SCS, FIU
Costs and Risks of the Database Approach
• New, Specialized Personnel
• Installation Management Cost and Complexity
• Conversion Costs
• Organizational Conflict