Chapter 2
description
Transcript of Chapter 2
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Computer Science CentreUniversity of Indonesia
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Chapter 2
Database System Concepts and Architecture
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Evolution of computing
• Database has evolved since nearly every stage of computing, from:– mainframes, which are monolithic– Client-server– Web-based
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Data Models
• A collection of concepts used to describe the structure of a database– Data types– Relationships– Constraints– Etc
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Categories of Data Models
• Conceptual data models: high level• Physical data models: how data is
actually stored in a disk• Representational data models:
somewhere between those two… let’s see…
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Representational data model• Relational data model (our main
discussion in this class)• Network data model (uses directed
graphs)• Hierarchial data model (history…)• Object data model (this is new!)
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Database schemas• Schemas: description of the database, but not the
database itself!• Example of a schema diagram:
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• Not included in the schema diagram above:– Data types?– Relationships?– Constraints, such as “students in CS
major must take CS1310…”
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Database states
• Also called ‘snapshot’• After we define, generaly a database
is at the ‘empty state’• We get the ‘initial state’ after we first
load the database• Valid state is a state which satisfies
the structure and constraints in the schema
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Three Schema Architecture• Internal schema: describes the
physical storage structure of the database
• Conceptual schema: structure of the whole database for a community of users
• External schemas for user views
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Data Independence
• Logical data independence: we can change the conceptual schema without changing the application program
• Physical data independence: we can change the internal schema without changing the conceptual schema. It might be because file database must be reorganized for fine tuning.
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Database Languages
• Data definition language• View definition language• Data manipulation language
– High level: SQL, set-at-a-time processing
– Low level: VB, COBOL, record-at-a-time processing
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DBMS Interfaces
• Menu based interface• Forms based interface• Graphical user interface• Natural language interface, you can
ask, “Show me all the students with GPA > 3”
• Parametric interface, such as xBase
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Database utilities
• Loading utility, or importer• Backup utility, usually to tape• File optimizer or reorganizer• Performance monitoring:
fragmentation, load balancing, etc.
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Classification of DBMS
• Single user vs multi user• Centralized vs distributed• Price…!• OLTP support?• OLAP support (read page 842)
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Computer Science CentreUniversity of Indonesia
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Group Assignment
Comparative Study of Popular DBMS
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Which ones?Group 1 (Haswar,
Conna, Vicky)• MySQL• MS-SQL Server• FoxPro
Group 2 (Fitri, al-Harith, Avi)
• MySQL• MS-SQL Server• IBM DB2
Group 3 (Danu, Lia, Narpati)
• Oracle database• Postgres• Borland Interbase
Group 4 (Armand, Tia, Aryo)
• FoxPro• MS-Access• Informix
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What to look for
• Use theories in chapter 1 & 2!
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Deliverables
• Presentatoin (of course)• Due next week• Paper, submitted to the TAs: Elan
and Amir (again…!)