Database concepts

Outline

 Database-System Applications
 Purpose of Database Systems
 View of Data
 Database Languages
 Database Design
 Database Engine
Chapter 1: Introduction  Database Architecture
 Database Users and Administrators
 History of Database Systems




Database System Concepts, 7th Ed.


LICET, CSE 1.2 ©Silberschatz, Korth, Sudarshan and GK




Database Systems Database Applications Examples

 DBMS contains information about a particular enterprise  Enterprise Information
• Collection of interrelated data • Sales: customers, products, purchases
• Set of programs to access the data • Accounting: payments, receipts, assets
• An environment that is both convenient and efficient to use • Human Resources: Information about employees, salaries, payroll
 Database systems are used to manage collections of data that are: taxes.

• Highly valuable  Manufacturing: management of production, inventory, orders, supply
chain.
• Relatively large
 Banking and finance
• Accessed by multiple users and applications, often at the same
time. • customer information, accounts, loans, and banking transactions.
 A modern database system is a complex software system whose task
• Credit card transactions
is to manage a large, complex collection of data. • Finance: sales and purchases of financial instruments (e.g., stocks
 Databases touch all aspects of our lives and bonds; storing real-time market data
 Universities: registration, grades




LICET, CSE 1.3 ©Silberschatz, Korth, Sudarshan and GK LICET, CSE 1.4 ©Silberschatz, Korth, Sudarshan and GK

, Database Applications Examples (Cont.) Purpose of Database Systems

 Airlines: reservations, schedules In the early days, database applications were built directly on top of file
 Telecommunication: records of calls, texts, and data usage, generating systems, which leads to:
monthly bills, maintaining balances on prepaid calling cards
 Data redundancy and inconsistency: data is stored in multiple file
 Web-based services formats resulting induplication of information in different files
• Online retailers: order tracking, customized recommendations  Difficulty in accessing data
• Online advertisements • Need to write a new program to carry out each new task
 Document databases  Data isolation
 Navigation systems: For maintaining the locations of varies places of • Multiple files and formats
interest along with the exact routes of roads, train systems, buses, etc.
 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




LICET, CSE 1.5 ©Silberschatz, Korth, Sudarshan and GK LICET, CSE 1.6 ©Silberschatz, Korth, Sudarshan and GK




Purpose of Database Systems (Cont.) University Database Example

 Atomicity of updates  In this text we will be using a university database to illustrate all the
concepts
• Failures may leave database in an inconsistent state with partial
updates carried out  Data consists of information about:
• Example: Transfer of funds from one account to another should either • Students
complete or not happen at all • Instructors
 Concurrent access by multiple users • Classes
• Concurrent access needed for performance  Application program examples:
• Uncontrolled concurrent accesses can lead to inconsistencies • Add new students, instructors, and courses
 Ex: Two people reading a balance (say 100) and updating it by • Register students for courses, and generate class rosters
withdrawing money (say 50 each) at the same time
• Assign grades to students, compute grade point averages (GPA) and
 Security problems generate transcripts
• Hard to provide user access to some, but not all, data

Database systems offer solutions to all the above problems




LICET, CSE 1.7 ©Silberschatz, Korth, Sudarshan and GK LICET, CSE 1.8 ©Silberschatz, Korth, Sudarshan and GK