Week 1 Flashcards
Examples of Database Application
Purchases from the supermarket
Purchases using your credit card
Booking a holiday at the travel agents
Using the local library
Taking out insurance
Renting a video
Using the Internet
Studying at university
File-based systems
Collection of application programs that perform services for the end users (e.g. reports).
Each program defines and manages its own data.
Limitations of File-Based Approach
Separation and isolation of data
Duplication of data
Data dependence
Incompatible file formats
Fixed Queries/Proliferation of application programs
Limitations of File-Based Approach
Separation and isolation of data
Duplication of data
Data dependence
Incompatible file formats
Fixed Queries/Proliferation of application programs
Database Approach
Arose because:
Definition of data was embedded in application programs, rather than being stored separately and independently.
No control over access and manipulation of data beyond that imposed by application programs.
Result:
the database and Database Management System (DBMS).
Database Approach
Arose because:
Definition of data was embedded in application programs, rather than being stored separately and independently.
No control over access and manipulation of data beyond that imposed by application programs.
Result:
the database and Database Management System (DBMS).
Database
Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.
System catalog (metadata) provides description of data to enable program–data independence.
Logically related data comprises entities, attributes, and relationships of an organization’s information.
Database Management System (DBMS)
A software system that enables users to define, create, maintain, and control access to the database.
(Database) application program: a computer program that interacts with database by issuing an appropriate request (SQL statement) to the DBMS.
Database Approach
Permits specification of data types, structures and any data constraints.
All specifications are stored in the database.
Data definition language (DDL).
Database Approach
General enquiry facility (query language) of the data.
Data manipulation language (DML).
Database Approach
Data definition language (DDL)
Data manipulation language (DML)
Database Approach
Data definition language (DDL)
Data manipulation language (DML)
Allows each user to have his or her own _____ of the database.
A _____ is essentially some subset of the database.
view
Allows each user to have his or her own _____ of the database.
A _____ is essentially some subset of the database.
view
Benefits of view
Reduce complexity
Provide a level of security
Provide a mechanism to customize the appearance of the database
Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed
