2. Advanced Database System
1.1 Introduction
A database system ⇒ a computerized record-keeping system
Operations:
1) adding new, empty files to the database
2) inserting data into existing files
3) retrieving data from existing files
4) deleting data from existing files
5) changing data in existing files
6) removing existing files from the database
(See Fig. 1.1, 1.2, & 1.3)
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5. 1.2 What is a Database System ?
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6. 1.2 What is a Database System ? (cont.)
Four components:
1) data ⇒ integrated & shared (See Fig. 1.5)
2) hardware ⇒ the second storage volumes,
the processors, & main memory
3) software ⇒ database management system (DBMS)
4) users ⇒ application programmers, end users, & database administrator (DBA)
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1.3 What is a Database ?
A database ⇒ persistent data
Entities & Relationships
Example: E/R diagram (See Fig. 1.6)
A number of points:
1) ternary relationship
2) one relationship involving just one entity type
3) more relationships between entities
Properties
Data and data models
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1.4 Why Database ?
Centralized control of data
Data administration (manager)
Database administration (technician)
Benefits of the database approach
The data can be shared
Redundancy can be reduced
Inconsistency can be avoided
Transaction support can be provided
Integrity can be maintained
Security can be enforced
Conflicting requirements can be balanced
Standards can be enforced
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1.5 Data Independence
The immunity of applications to change in physical representation and access technique
Stored field, stored record, stored file (See Fig. 1.7)
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11. 1.6 Relational Systems and Others
The oldest systems:
Inverted list
Hierarchic
Network
Relation systems: DB2, Ingres II, Informix Dynamic Server,
Microsoft SQL server, Oracle 9i, Sybase Adaptive Server
(See Fig. 1.8)
Object systems: GemStone, Versant ODBMS
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The End.
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