1. 28 Database Theory 28

2. Database Theory We have looked at the basics of how databases work: Database Tables A A Relational Databases C C Types of Data B B

3. 28 Database Theory Database Tables A A Relational Databases C C Types of Data B B Now we’re going to look at a practical example of a relational database:

4. 28 Database Theory Simple databases with just one data table are called flat file databases. But using only one table creates BIG problems for larger systems because lots of data can be duplicated and the database becomes very inefficient. So advanced databases use multiple tables They are called relational databases Relational Databases C C

5. 28 Database Theory Typical exam question: Explain the relationships between the Hire table and the other two tables. [2] Explain one advantage to the car hire company of using a relational database rather than a single table. [2]

6. 28 Database Theory Adding new records in Flat Files & Relational Databases

7. 28 Database Theory Start by looking at the data in a flat file What does this mean?

8. 28 Database Theory FIESTA KA MONDEO GOLF Mr SmithMr BakerMiss Green Mrs Brown 15 Fri May 14 Thu Jul 14 Thu Jul 16 Sat May 15 Fri Jul 17 Sun May 16 Sat May 15 Fri Jul Is hired for two days… …by Mr Smith Is hired for one day… …by Miss Green Is hired for two days… …by Mrs Brown Is hired for three days… …by Mr Baker

9. 28 Database Theory We’re about to add some new hire arrangements. You’ll need to know about how the HireIDs are made… HireID Starts with an H First letter of car model Day and month of hire HG147 H for HireG for Golf147 for 14 th July

10. 28 Database Theory Add the new arrangements to the table AB10 WXYFordFiesta£12kManualHF22722/7/152 daysGRE81Miss Green7 Long Row, NewtonLA2 8KE015395 12356

11. 28 Database Theory GOLF Mr SmithMiss Green 17 Thu May 16 Wed May 19 Tue Jul Mr Baker MONDEO Miss Green FIESTA MONDEO 15 Sat May 22 Fri Jul 18 Mon Jul 16 Mon May 17 Sun Jul Is hired for two days… …by Miss Green Is hired for one day… …by Mr Baker Is hired for three days… …by Miss Green Is hired for two days… …by Mr Smith

12. 28 Database Theory Mrs Brown MONDEO KA Mr Smith FIESTA KA Mrs Brown Miss Green 16 Thu May 27 Wed Jul 25 Mon Jul 26 Tue Jul 16 Wed May 16 Tue May 25 Mon Jul Is hired for one day… …by Mrs Brown Is hired for one day… …by Mr Smith Is hired for two days… …by Miss Green Is hired for three days… …by Mrs Brown

13. 28 Database Theory You end up with…

14. 28 Database Theory Look at the same data in a relational database For now, we’re just looking at the tables on the bottom of the sheet…

15. 28 Database Theory Add the new arrangements… AB10 WXY HF22722/7/15 2 days GRE81

16. 28 Database Theory GOLF Mr SmithMiss Green 17 Thu May 16 Wed May 19 Tue Jul Mr Baker MONDEO Miss Green FIESTA MONDEO 15 Sat May 22 Fri Jul 18 Mon Jul 16 Mon May 17 Sun Jul Is hired for two days… …by Miss Green Is hired for one day… …by Mr Baker Is hired for three days… …by Miss Green Is hired for two days… …by Mr Smith

17. 28 Database Theory Mrs Brown MONDEO KA Mr Smith FIESTA KA Mrs Brown Miss Green 16 Thu May 27 Wed Jul 25 Mon Jul 26 Tue Jul 16 Wed May 16 Tue May 25 Mon Jul Is hired for one day… …by Mrs Brown Is hired for one day… …by Mr Smith Is hired for two days… …by Miss Green Is hired for three days… …by Mrs Brown

18. 28 Database Theory All the new arrangements… If we’d had any new customers, we’d add them in this table If we’d had any new cars, we’d add them in this table …are in the Hire table

19. 28 Database Theory Making changes in Flat Files & Relational Databases

20. 28 Database Theory Start with the Flat File

21. 28 Database Theory Miss Green has just phoned… …she is getting married so please update her name to Mrs Gage Mr Smith is moving house… …please change his details to 8 Low Road, Kirkby, LA6 2RP, 015242 789321

22. 28 Database Theory Changes in a Flat File Miss GreenMr Smith

23. 28 Database Theory Now look at the same changes here:

24. 28 Database Theory Miss Green has just phoned… …she is getting married so please update her name to Mrs Gage Mr Smith is moving house… …please change his details to 8 Low Road, Kirkby, LA6 2RP, 015242 789321

25. 28 Database Theory Changes in a Relational Database Miss GreenMr Smith

26. 28 Database Theory Advantages of Relational Databases Less duplication (redundancy) Fewer errors (inconsistencies) Easier to make changes More efficient

27. 28 Database Theory Talking about relationships in Relational Databases

28. 28 Database Theory This is a ?? This is a ?? Recordl Field All this data is stored in a ?? Table This is a ?? This is a ?? Field name This is the ?? Primary Key Re-cap…

29. 28 Database Theory DocID Foreign Key PatientID Primary Key DocID Primary Key Relational Databases C C

30. 28 Database Theory Identify the primary and foreign keys: Primary key Foreign key A table that links other tables, is called a Link table. Link Table

31. 28 Database Theory Describing the relationships: One customer can arrange many hires One car can be hired many times A one-to-many relationship One customer can arrange many hires One car can be hired many times

32. 28 Database Theory Patients Patient ID Forename Surname DocID Doctors DocID Surname Department Mobile We’ve seen this before… It’s a ‘One To Many’ relationship One doctor can treat many patients

33. 28 Database Theory Let’s go back to the question…

34. 28 Database Theory Can we answer these now? Explain the relationships between the Hire table and the other two tables. [2] Explain one advantage to the car hire company of using a relational database rather than a single table. [2]

35. 28 Database Theory

36. 28 Database Theory