1. Unit 5 Advanced Databases The Purpose and features of a relational database

2. Aims Discuss what is a database Discuss purpose and features of a relational database Learn some terminology focused around databases

3. What is a Database? A database is a structured collection of records or data that is stored in a computer system. The structure is achieved by organizing the data according to a database model. http://en.wikipedia.org/wiki/Database A collection of information organized in such a way that a computer program can quickly select desired pieces of data. You can think of a database as an electronic filing system. http://www.webopedia.com/TERM/d/database.html

4. Examples? Library Movie rental College There are loads….

5. What is the main purpose of a database? Store information efficiently and reliably so that the information can be retrieved on demand in the form and structure required. Databases are designed for three main purposes. These are to organize, store, and retrieve information as efficiently and effectively as possible. Probably the retrieval of information is the most important of these three. It doesn't matter how well your database stores information if you can never get it back out again. It would be like having a piggy bank full of money that you couldn't open. But unlike a piggy bank, breaking the computer doesn't release the information. http://www.mchenry.edu/library/tutorial/Purpose.htm

6. Purposes Cont. Minimise unnecessary data redundancy (duplications) Ease of modification Simple design Keep data consistent, data is only stored once Can represent real world entities

7. Types of databases Using the internet find out about the following types of databases: Flat file – A flat file database is a database designed around a single table. Relational database – Incorporates multiple tables that are related together using keys. 10 minutes

8. Relational databases Some of the features of a relational database are outlined below: Use of simple named tables to store information Quick and structured searches can be performed, due to the table relationships and minimised redundancy. Data can be more easily managed by being able to use facilities like Cascade Update / Delete. This keeps all record relationships up-to- date i.e. if the primary key was changed in the primary table all records related to that record is updated with the new primary key value. If a primary record was deleted all related records are also deleted to minimise redundant data. Security can be set to enable different users to access different levels of the database Less time is required re-entering data because the same data can be linked to records via a primary / foreign key.

9. Relational databases Using the internet find out what the following terms mean? Field Column Row Primary Key Foreign Key Atomic Entity Table Data redundancy 25 minutes Extra Task: Normalisation

10. Terminology Table The data values held are stored in the tables A table has rows and columns. Each column represents a particular data value, e.g. Author. Each row represents a record of a “thing”, e.g. Book Book IDTitleAuthorPublisher 0001FishingJ P JonesBookit 0002SewingP R Green Morebook 0003FootballG K Singh Bookit Column Row

11. Terminology Entity An entity is a name of some part of the data chosen so that it can be referenced by a name. In this example the entities are the same as the tables. For example: Student, Book

12. Terminology Attribute / Field An item of data relating to an entity e.g. Company name. What are the other attributes in this example? Book IDTitleAuthorPublisher 0001FishingJ P JonesBookit 0002SewingP R GreenMorebook 0003FootballG K SinghBookit

13. A school or college library lends books Book IDTitleAuthorPublisher 0001FishingJ P JonesBookit 0002SewingP R GreenMorebook 0003FootballG K SinghBookit to students. Student IDLast nameFirst nameForm 0103SimonsMichael12H 0104ChanPeggy12N Quick Quiz

14. Conclusion Discussed what is a database Discussed purpose and features of a relational database Learnt some terminology focused around databases