customers, accounts, bank branch Relationships between entities E.g. Views can also hide information (e.g., salary) for security purposesĦ Data Models A collection of tools for describing data data relationships data semantics data constraints Entity-Relationship model Relational model Other models: object-oriented model semi-structured data models Older models: network model and hierarchical model 1.11 Entity-Relationship Model Example of schema in the entity-relationship modelħ Entity Relationship Model (Cont.) E-R model of real world Entities (objects) E.g. type customer = record name : string street : string city : integer end View level: application programs hide details of data types. Logical level: describes data stored in database, and the relationships among the data. two people reading a balance and updating it at the same time Security problems Database systems offer solutions to all the above problems 1.7 Levels of Abstraction Physical level describes how a record (e.g., customer) is stored. 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 E.g.
BASIC CONCEPT OF DATABASE MANAGEMENT SYSTEM PDF CODE
account balance > 0) become part of program code Hard to add new constraints or change existing ones 1.6 3Ĥ 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 E.g. Database Applications: Banking: all transactions Airlines: reservations, schedules Universities: registration, grades Sales: customers, products, purchases Manufacturing: production, inventory, orders, supply chain Human resources: employee records, salaries, tax deductions Databases touch all aspects of our lives 1.5 Purpose of Database System In the early days, database applications were built 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. Gardarin Ramakrishnan) 1.2 1Ģ What we are going to see Introduction to database management systems What's inside Why it's interesting Relational databases: the success story in databases Relational model Relational algebra Most successful relational query language: SQL Most successsful commercial product implementing SQL: Oracle 1.3 Chapter 1: Introduction Purpose of Database Systems View of Data Data Models Data Definition Language Data Manipulation Language Transaction Management Storage Management Database Administrator Database Users Overall System Structure 1.4 2ģ Database Management System (DBMS) Collection of interrelated data Set of programs to access the data DBMS contains information about a particular enterprise DBMS provides an environment that is both convenient and efficient to use. Sudarshan (minor modifications to slides) All slides are at: The content taught here is basic and can be found in many other good books (e.g. 1 Introduction to database management systems Database management systems module Myself: researcher in INRIA Futurs, The course: follows (part of) the book "", Fourth Edition Abraham Silberschatz, Henry F.