1.3.2 Databases
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What is a database?
An organised collection of data Allows easy storage, retrieval and management of data
What are the benefits of an electronic database?
Easier to add, delete and modify data Data can be backed up and copied easier Multiple users can access it from various locations
What is a field?
A single piece of data in a record
What is a record?
A group of related fields representing one data entry
What is a table?
A collection of records with a similar structure
What is a primary key?
A unique identifier for each record in a table, usually an ID number
What is a compound primary key?
A combination of 2 or more fields that is unique for all records
What is a foreign key?
A field that refers to a primary key in another table Used to link tables and create relationships
What is a secondary key?
A field or fields that are indexed for faster searching
What is database management system (DBMS)
Software used to manage databases
What is indexing?
A technique used to speed up searching and retrieving data in a database
What is a flat file database?
When data is all stored in the same table
What are the benefits of flat file databases?
Simple and easy to understand
What are the drawbacks of flat file databases?
Causes data redundancy Inefficient storage Harder to maintain
What is a relational database?
A database that organises data into multiple tables Uses keys to connect related data
What are the benefits of relational databases?
Reduces data redundancy Efficient use of storage Easier to maintain
What is normalisation?
The process of organising databases to reduce data duplication and improve data accuracy and consistency Applies a set of guidelines (forms)
What is first normal form?
-Contains atomic values (each value must be single values) -Have no repeating groups (columns must not contain lists of values) -Have unique column names -Have a primary key
What is second normal form?
-Must be in 1NF -Only applies to tables with a compound primary key -All attributes must be dependent on the primary key
What is a compound primary key?
A combination of 2 or more fields that is unique for all records
What is third normal form?
-Must be in 2NF -Attributes must only depend on the primary key
What is an entity?
Something worth capturing and storing data about Becomes a table in relational databases
What are the 3 types of relationships?
-One - One -One to many -Many - many
How can data be captured?
-Forms -Optical mark recognition -Optical character recognition -Sensors -Barcodes -Data mining