Unit 5

Conceptual data model - describes how data elements in the system are to be grouped

Entity - thing of interest about which data is to be held

Attribute - property or characteristic of an entity

Relationship - link or association between entities

Entity-relationship diagram - diagrammatic way of representing the relationship between the entities in a database

Problems with the traditional file approach:-

Database - collection of non-redundant data sharable between different applications

Problems with the database approach:-

Database Management System (DBMS)

Relational database

Foreign key - primary key from one table used as foreign key in a second table (common field)


First normal form - no repeating attributes or groups of attributes

Second normal form - in first normal form and no attribute that is not part of the primary key is dependent on only a portion of the primary key

Third normal form - no non-key dependencies (Boyce-Codd Normal Form - BCNF)

SQL (Structured Query Language) - data access language which deals with the manipulation of tables and data

DML (Data Manipulation Language) - the part of SQL concerned with asking questions of a database

Schema - different levels or views from which a database may be considered

DDL (Data Definition Language)

DML (Data Manipulation Language) - provides comprehensive set of commands to allow modification of the data within a database

VALUES ('Harry', 'Washington', 'Trainee')

Open systems - provide a standard by which applications may be written to allow portability to multiple systems

OBDC (Open Database Connectivity)

Database Mnagement System (DBMS)

Data dictionary - a database about the database

Multi-access database - more than one person can view and update the same tables concurrently

Ensuring integrity - ensuring no data is lost or corrupted (making sure updates are not lost)

Deadlock (Deadly embrace)

Software protection techniques

Client-server database

Object-oriented database - stores the data and methods as objects that can be automatically retrieved and shared (more suited to handling graphics based or multimedia applications)