Databases

Databases

• Key Vocabulary
• database
• key field
• record
• field
• relational databases
• primary key
• foreign key
• data integrity
• reports
• digital data
• analogue data
• query
• data types (e.g. number, alphanumeric...)
• field properties (e.g. field size, input mask...)
• 
• Legenda: Database: E.g. relational database

Introduction

• DATABASE- a collection of information which is structured in the same way to permit manipulation and searching data
• Why are databases used?
• data consistency - when data is updated on it is up-to-date for any application which uses the database
• data duplication - reduces to a minimum since only one copy of each data item needs to be kept
• easy to expand the database
• security of data is easier to monitor and maintain
• 
• Legenda: data consistency / up-to-date for any application

Security

• 
• Legenda: Data access can be controlled by database FRONT ENDS; the actual database won't be seen by other users except the database administrator

Data Structures

• Data is often stored in FILES, which consist of RECORD, which in turn consist of FIELDS
• KEY FIELD - contains and item of data that is unique to that record; so no records have the same value in the key field
• RECORD - composed of fields, each containing one type of information
• FIELD - a space allocated for a particular item of information
• 
• Legenda: Data Structure

Relational Database

• RELATIONAL DATABASE - it consists of a number of separate tables which are related
• PRIMARY KEY - a combination of columns that are designated to uniquely identify all table records
• Advantages :
• they do not need to repeat data
• information is stored in separate tables only connected by the primary key field
• faster data retrieved (because of links between tables)
• easy expansion
• DATA INTEGRITY - all other references to this data will be up-to-date by only editing one table
• 
• Legenda: relational database

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