Database 2
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Transcript of Database 2
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1Chapter 1
Lecture 2
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2Chapter 1
Disadvantages of File Processing
• Program-Data Dependence– All programs maintain metadata for each file they use
• Duplication of Data– Different systems/programs have separate copies of the same data
• Limited Data Sharing– No centralized control of data
• Lengthy Development Times– Programmers must design their own file formats
• Excessive Program Maintenance– 80% of information systems budget
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3Chapter 1
SOLUTION: The DATABASE Approach
• Central repository of shared data• Data is managed by a controlling
agent• Stored in a standardized, convenient
form
Requires a Database Management System (DBMS)
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4Chapter 1
Database Management System
DBMS manages data resources like an operating system manages hardware resources
• A software system that is used to create, maintain, and provide controlled access to user databases
Order Filing System
Invoicing System
Payroll System
DBMSCentral database
Contains employee,order, inventory,
pricing, and customer data
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5Chapter 1
Advantages of the Database Approach• Program-data independence• Planned data redundancy• Improved data consistency• Improved data sharing• Increased application development productivity• Enforcement of standards• Improved data quality• Improved data accessibility and responsiveness• Reduced program maintenance• Improved decision support
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6Chapter 1
Costs and Risks of the Database Approach
• New, specialized personnel• Installation and management cost and
complexity• Conversion costs• Need for explicit backup and recovery• Organizational conflict
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7Chapter 1
Elements of the Database Approach
• Data models – Graphical system capturing nature and relationship of data– Enterprise Data Model–high-level entities and relationships for
the organization– Project Data Model–more detailed view, matching data structure
in database or data warehouse • Relational Databases
– Database technology involving tables (relations) representing entities and primary/foreign keys representing relationships
• Use of Internet Technology– Networks and telecommunications, distributed databases, client-
server, and 3-tier architectures• Database Applications
– Application programs used to perform database activities (create, read, update, and delete) for database users
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8Chapter 1
Segment of an Enterprise Data Model
Segment of a Project-Level Data Model
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9Chapter 1
One customer may place many orders, but each order is placed by a single customer
One-to-many relationship
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10Chapter 1
One order has many order lines; each order line is associated with a single order
One-to-many relationship
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11Chapter 1
One product can be in many order lines, each order line refers to a single product
One-to-many relationship
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12Chapter 1
Therefore, one order involves many products and one product is involved in many orders
Many-to-many relationship
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13Chapter 1
Figure 1-4 Enterprise data model for Figure 1-3 segments
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14Chapter 1
Figure 1-5 Components of the Database Environment
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15Chapter 1
Components of the Database Environment
• CASE Tools–computer-aided software engineering• Repository–centralized storehouse of metadata• Database Management System (DBMS) –software for
managing the database• Database–storehouse of the data• Application Programs–software using the data• User Interface–text and graphical displays to users• Data/Database Administrators–personnel responsible
for maintaining the database• System Developers–personnel responsible for
designing databases and software• End Users–people who use the applications and
databases
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16Chapter 1
The Range of Database Applications
• Personal databases• Workgroup databases• Departmental/divisional databases• Enterprise database
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17Chapter 1
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18Chapter 1
Figure 1-6Typical data from a personal database
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19Chapter 1
Figure 1-7 Workgroup database with wireless local area network
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20Chapter 1
Enterprise Database Applications
• Enterprise Resource Planning (ERP)– Integrate all enterprise functions
(manufacturing, finance, sales, marketing, inventory, accounting, human resources)
• Data Warehouse– Integrated decision support system derived
from various operational databases
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21Chapter 1
Figure 1-8 An enterprise data warehouse
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22Chapter 1
Evolution of DB Systems