ch1 - Database System Concepts 5th Ed ©Silberschatz Korth...

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Unformatted text preview: Database System Concepts, 5th Ed . ©Silberschatz, Korth and Sudarshan See www.db-book.com for conditions on re-use Chapter 1: Introduction Chapter 1: Introduction ©Silberschatz, Korth and Sudarshan 1.2 Database System Concepts - 5 th Edition, May 23, 2005 Chapter 1: Introduction Chapter 1: Introduction ■ Purpose of Database Systems ■ View of Data ■ Database Languages ■ Relational Databases ■ Database Design ■ Object-based and semistructured databases ■ Data Storage and Querying ■ Transaction Management ■ Database Architecture ■ Database Users and Administrators ■ Overall Structure ■ History of Database Systems ©Silberschatz, Korth and Sudarshan 1.3 Database System Concepts - 5 th Edition, May 23, 2005 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: all 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 1.4 Database System Concepts - 5 th Edition, May 23, 2005 Purpose of Database Systems Purpose of Database Systems ■ In the early days, database applications were built directly on top of file 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 - 5 th Edition, May 23, 2005 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 accessed needed for performance Uncontrolled concurrent accesses can lead to inconsistencies – Example: Two people reading a balance and updating it 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 1.61....
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This note was uploaded on 02/17/2010 for the course CAS 6M03 taught by Professor Franek during the Spring '10 term at McMaster University.

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ch1 - Database System Concepts 5th Ed ©Silberschatz Korth...

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