Lesson Objectives Aims You should know about: 1.3.2: (a) Relational database, flat file, primary key, foreign key, secondary key, entity relationship modelling, normalisation and indexing.

Databases We have an important equation for you to learn: Socks + Sandals = Beard

First, a story Until the late 1970’s, business really failed to see the point in computers There were no: –Databases –Internet –Large scale networks There were: –Lots of people paid to create and shuffle large amounts of paper!

Fast forwards… Then a goldilocks condition came about: –Mass storage became large, abundant and cheap –Processing power increased exponentially –The internet connected the world together –Companies realised the power of mass data (warehousing and mining)

Data Capture OCR – Google books! OMR – Lottery tickets, tests, surveys Direct entry/web entry

Database Terms Field/Attribute – A single attribute of an item or object. E.g. Weight Record – All related attributes describing one single object Table – A collection of all related records

Flat file database Student IDStudent name GenderDOBCourse IDCourse nameTeacher IDTeacher name Teacher specialism 67678Jim Donaldson M30/01/2000GY51Mathematics4445Mr SurrallMathematics 67677Jane JonesF02/01/2000FU451Physics4445Mr SurrallMathematics 67678Jim Donaldson M30/01/2000F4IO52Computer Science 4433Mr SmithPhysics 67222Lucy KidF08/03/2000GY51Mathematics4445Mr SurrallMathematics All data held in one single table Small/Simple databases Problem with redundancy –Update issues –Potentially even legal issues

Relational Database Data split in to several tables Tables are linked through relationships These are called primary and foreign keys Removes the issue of redundancy (largely) More difficult to create and maintain

Relational example

Some more key terms Primary key - A piece of information in each record that is unique to that record - a ‘unique identifier’. Primary keys are usually ID numbers generated especially for that purpose. Enables/guarantees a record can be found / item can be reliably identified Customer numbers, account numbers are classic examples. The primary key is used to link two records together.

More terms… Foreign key - any field in a table which is the primary key in another table. Secondary key - an additional key (or alternate key ) which can be used to search for a record in a database. Unlike the primary key, it does not need to be unique to a particular record. May be used to create a “composite key”

Review/Success Criteria You should know: The two main types of database Key database terms Why databases are necessary