UNIT I - DATA BASE SYSTEM CONCEPT
File systems - Database systems - Database systems architecture - Data models - Relational model – Hierarchical model - Network model - Entity-Relationship model - Data Dictionary - Database Administration and control.
Database Management System (DBMS)
©Collection of interrelated data: database
©Set of programs to store, access, maintain the data: DBMS
©DBMS handles information about a particular enterprise
©DBMS provides an environment that is simultaneously convenient, secure and efficient to use.
©Database applications handle information components:
§Banking: all business 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 most aspects of our lives
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. account balance > 0) become part of program code
¨Hard to add new constraints or change existing ones
Levels of Abstraction
©Physical level: (“internal” level) describes how a record (e.g., customer) is stored, indexed, sorted, …
©Logical level: (“conceptual” level) describes data types stored in database, and the relationships among the data types.
type customer = record name : string; street : string; city : integer; end;
©View level: (“external” level) hides details of data types from application programs. Views can also hide information (e.g. salary data) for security or privacy purposes.
View of Data
An architecture for a database system
File systems - Database systems - Database systems architecture - Data models - Relational model – Hierarchical model - Network model - Entity-Relationship model - Data Dictionary - Database Administration and control.
Database Management System (DBMS)
©Collection of interrelated data: database
©Set of programs to store, access, maintain the data: DBMS
©DBMS handles information about a particular enterprise
©DBMS provides an environment that is simultaneously convenient, secure and efficient to use.
©Database applications handle information components:
§Banking: all business 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 most aspects of our lives
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. account balance > 0) become part of program code
¨Hard to add new constraints or change existing ones
Levels of Abstraction
©Physical level: (“internal” level) describes how a record (e.g., customer) is stored, indexed, sorted, …
©Logical level: (“conceptual” level) describes data types stored in database, and the relationships among the data types.
type customer = record name : string; street : string; city : integer; end;
©View level: (“external” level) hides details of data types from application programs. Views can also hide information (e.g. salary data) for security or privacy purposes.
View of Data
An architecture for a database system
