ch1_Intro

ch1_Intro - Silberschatz, Korth and Sudarshan 1.1 Database...

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Unformatted text preview: Silberschatz, Korth and Sudarshan 1.1 Database System Concepts - 6 th Edition Chapter 1: Introduction Chapter 1: Introduction Silberschatz, Korth and Sudarshan 1.2 Database System Concepts - 6 th Edition Database Management System (DBMS) Database Management System (DBMS) DBMS contains information about a particular enterprise Collection of interrelated data Set of programs to access the data An environment that is both convenient and efficient to use Database Applications: Banking: transactions Airlines: reservations, schedules Universities: registration, grades Sales: customers, products, purchases Online retailers: order tracking, customized recommendations Manufacturing: production, inventory, orders, supply chain Human resources: employee records, salaries, tax deductions Databases touch all aspects of our lives Silberschatz, Korth and Sudarshan 1.3 Database System Concepts - 6 th Edition University Database Example University Database Example Application program examples Add new students, instructors, and courses Register students for courses, and generate class rosters Assign grades to students, compute grade point averages (GPA) and generate transcripts In the early days, database applications were built directly on top of file systems Silberschatz, Korth and Sudarshan 1.4 Database System Concepts - 6 th Edition Purpose of Database Systems Purpose of Database Systems Drawbacks of using file systems to store data: Data redundancy and inconsistency Multiple file formats, duplication of information in different files Difficulty in accessing data Need to write a new program to carry out each new task Data isolation multiple files and formats Integrity problems Integrity constraints (e.g., account balance > 0) become buried in program code rather than being stated explicitly Hard to add new constraints or change existing ones Silberschatz, Korth and Sudarshan 1.5 Database System Concepts - 6 th Edition Purpose of Database Systems (Cont.) Purpose of Database Systems (Cont.) Drawbacks of using file systems (cont.) Atomicity of updates Failures may leave database in an inconsistent state with partial updates carried out Example: Transfer of funds from one account to another should either complete or not happen at all Concurrent access by multiple users Concurrent access needed for performance Uncontrolled concurrent accesses can lead to inconsistencies Example: Two people reading a balance (say 100) and updating it by withdrawing money (say 50 each) at the same time Security problems Hard to provide user access to some, but not all, data Database systems offer solutions to all the above problems Silberschatz, Korth and Sudarshan 1.6 Database System Concepts - 6 th Edition Levels of Abstraction Levels of Abstraction Physical level: describes how a record (e.g., customer) is stored.describes how a record (e....
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This note was uploaded on 09/10/2011 for the course CS 308 taught by Professor Frankl during the Spring '11 term at NYU Poly.

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ch1_Intro - Silberschatz, Korth and Sudarshan 1.1 Database...

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