A database usually holds large collection of data organised especially for rapid search and retrieval.
A database is a logically coherent collection of data with some inherent meaning.
Data is raw facts and figures stored as independent units.
Information is data given context and meaning. It has been processed.
Data à Information =
-E.g. Find Average
-E.g. work out VAT.
Databases can be used to share data with different computers and users.
It can also be used as reliable storage which can be accessed.
Efficiency and optimised.
Don’t need to care about physical formats.
They can also be used for communication.
File based system – redundancy and synchronisation issues.
File based systems are application focused.
Easy to create
Fast for specialised tasks
Centralised data definitions
Centralised access control
A database is a centralised store of data.
- Single repository of data
Independent of individual applications
- No one application dictates use
- Contains a description of itself
Designing the database:
Model data first – getting the requirements from users.
Design a single logical model of the data.
Identifies entities and relationships.
Database management software:
DBMS is the software which manages the database.
It sits between the application and the data.
- Making changes to the structure of the data
- Manipulating the data
- Accessing the data
People who work with DBMS:
- Database Admins
- Application developers
- End users
Types of DBMS:
- Relational (main one for us!)
- Object relational
- Data redundancy
- Data consistency
- Data integrity
- Adherence to standards
- Control of security and access
Idealised database development systems:
Databases are a part of information systems.
The database may be divided into levels/steps
- Conceptual level (understand)
- Logical level (design)
- Physical level (implement)
We may need modelling techniques:
- Entity-relationship models
- Relational data models
Definition à Requirements à Design à Implementation à Testing à Maintenance
Good data models:
- Structural validity
- Share ability
- Diagrammatic representation
File à Stores data in a system
Database à Large store of related data
DBMS à Program for managing system
User à Person who accesses data in a database
Data model à Description of data
A relational system is a system in which: