Database Applications Examples Enterprise Information Sales:customers,products,purchases Accounting:payments,receipts,assets Human Resources:Information about employees,salaries,payroll taxes. ■ Manufacturing:management of production,inventory,orders,supply chain. Banking and finance customer information,accounts,loans,and banking transactions. Credit card transactions Finance:sales and purchases of financial instruments (e.g.,stocks and bonds;storing real-time market data Universities:registration,grades Database System Concepts-7th Edition 1.4 ©Silberscha乜，Korth and Sudarshan
Database System Concepts - 7 1.4 ©Silberschatz, Korth and Sudarshan th Edition Database Applications Examples ▪ Enterprise Information • Sales: customers, products, purchases • Accounting: payments, receipts, assets • Human Resources: Information about employees, salaries, payroll taxes. ▪ Manufacturing: management of production, inventory, orders, supply chain. ▪ Banking and finance • customer information, accounts, loans, and banking transactions. • Credit card transactions • Finance: sales and purchases of financial instruments (e.g., stocks and bonds; storing real-time market data ▪ Universities: registration, grades
Database Applications Examples (Cont.) Airlines:reservations,schedules Telecommunication:records of calls,texts,and data usage,generating monthly bills,maintaining balances on prepaid calling cards Web-based services Online retailers:order tracking,customized recommendations Online advertisements Document databases Navigation systems:For maintaining the locations of varies places of interest along with the exact routes of roads,train systems,buses,etc. Database System Concepts-7th Edition 1.5 @Silberschatz,Korth and Sudarshan
Database System Concepts - 7 1.5 ©Silberschatz, Korth and Sudarshan th Edition Database Applications Examples (Cont.) ▪ Airlines: reservations, schedules ▪ Telecommunication: records of calls, texts, and data usage, generating monthly bills, maintaining balances on prepaid calling cards ▪ Web-based services • Online retailers: order tracking, customized recommendations • Online advertisements ▪ Document databases ▪ Navigation systems: For maintaining the locations of varies places of interest along with the exact routes of roads, train systems, buses, etc
Purpose of Database Systems In the early days,database applications were built directly on top of file systems,which leads to: Data redundancy and inconsistency:data is stored in multiple file formats resulting induplication 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 Database System Concepts-7th Edition 1.6 ©Silberscha乜，Korth and Sudarshan
Database System Concepts - 7 1.6 ©Silberschatz, Korth and Sudarshan th Edition Purpose of Database Systems ▪ Data redundancy and inconsistency: data is stored in multiple file formats resulting induplication 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 In the early days, database applications were built directly on top of file systems, which leads to:
Purpose of Database 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 Ex: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 Database System Concepts-7th Edition 1.7 ©Silberscha乜，Korth and Sudarshan
Database System Concepts - 7 1.7 ©Silberschatz, Korth and Sudarshan th Edition Purpose of Database 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 ▪ Ex: 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
Data Models A collection of tools for describing 。Data ·Data relationships ·Data semantics ·Data constraints ■Relational model Entity-Relationship data model(mainly for database design) Object-based data models (Object-oriented and Object-relational) Semi-structured data model (XML) ■Other older models: ·Network model ·Hierarchical model Database System Concepts-7th Edition 1.10 ©Silberscha乜，Korth and Sudarshan
Database System Concepts - 7 1.10 ©Silberschatz, Korth and Sudarshan th Edition Data Models ▪ A collection of tools for describing • Data • Data relationships • Data semantics • Data constraints ▪ Relational model ▪ Entity-Relationship data model (mainly for database design) ▪ Object-based data models (Object-oriented and Object-relational) ▪ Semi-structured data model (XML) ▪ Other older models: • Network model • Hierarchical model