1. Relational Data Analysis II

2. Plan Introduction Structured Methods –Data Flow Modelling –Data Modelling –Relational Data Analysis Feasibility Maintenance

3. Definitions A relation corresponds to a table A tuple is a row in a table An attribute is a column in a table A Primary Key is the attribute by which we uniquely identify each row The number of rows in a table is called the cardinality The number of attributes in a table is called the degree

4. Example Relation (Table) Student ID Student Name CourseModule Code Module Name Grade 1000001Peter Stringfellow BSc Basket Weaving W1001Flower Arranging A 1001234Terrence Halfwit BA Surfing Studies S2003Hazardous Fishes B 1234567Big JohnBSc BusinessB3333Selling StuffE 1234567Big JohnBSc BusinessB3334Buying StuffA Student

5. Example Relation (Table) The table can also be described without its data as follows: Student (Student ID, Student Name, Course, Module Code, Module Name, Grade) Or Student ID Student Name Course Module Code Module Name Grade

6. Rules No two rows in a table are identical –i.e. there are no duplicate tuples/rows Every relation has a Primary Key attribute Each tuple has a primary key value The sequence of the rows should not be significant The sequence of the columns should not be significant Each attribute must have a unique name

7. Problems with Tables Problems with tables can be classified into three groups: –Insert Anomalies – Problems caused when inserting new information –Update Anomalies – Problems caused when updating existing data –Delete Anomalies – Problems caused when deleting data

8. The Solution? To remove these anomalies we must re- arrange the data and create new tables The process for doing this is called Normalisation

9. First Normal Form All data in a table must be dependant on the key In order to do this we must remove “repeating groups” This is done by analysing the relationship between the primary key and the rest of the data

10. Example 1 - Students Student ID Student Name Course Course ID Module Code Module Name Grade Attributes are moved if there is more than one for each instance of the primary key

11. Example 1 - Students Student ID Student Name Course Course ID Module Code Module Name Grade For each Student ID How many Student names are there? 1 or Many?

12. Example 1 - Students Student ID Student Name Course Course ID –Module Code Module Name Grade For each Student ID How many Module Codes are there?

13. Example 1 - Students Student ID Student Name Course Course ID –Module Code –Module Name –Grade Indented data is a repeating group We need to put it into a new table This table will describe the module a student is taking We will call it Student Module

14. Example 1 - Students Student ID Student Name Course Course ID Student ID Module Code Module Name Grade We now have two tables Student details –Primary Key = Student ID Student’s module details –PK = Student ID, Module Code –Called a compound Key

15. Yes… But… No… But… There are still Anomalies… Update –Cannot change a module name without finding all students on it Insert –Cannot add a new module unless we have a student enrolled Delete –When a student leaves we could lose course information Further Normalisation is therefore required…

16. Example 2 - Library Student ID Name Faculty Book ID Title Author Return Date Put this data into First Normal Form

17. Example 2 - Library Student ID Name Faculty –Book ID –Title –Author –Return Date Identify Repeating group

18. Example 2 - Library Student ID Name Faculty Student ID Book ID Title Author Return Date Create a New table Remember to keep the original PK in that of the new table This maintains the relationship between the two tables

19. Example 3 Customer ID Customer Name Address Branch No Branch Manager Stock ID Title Format Put this data into First Normal Form

20. Example 3 Customer ID Customer Name Address Branch No Branch Manager –Stock ID –Title –Format Identify Repeating group

21. Example 3 – Borrowing Videos Customer ID Customer Name Address Branch No Branch Manager Customer ID Stock ID Title Format Create New table

22. Remember 1NF can be considered as Normalised But it doesn’t solve all of our problems

23. Second Normal Form Only Applies to tables with compound keys Data in a table must depend on the whole key We must remove any partial dependencies

24. Example 1 – Students (1NF) Student ID Student Name Course Course ID Student ID Module Code Module Name Grade This table is already in 1NF as it does not have a compound key This table may not be in 2NF Need to analyse the relationship between attributes and the key

25. Example 1 – 2NF Student ID Module Code Module Name Grade Examine the attribute ‘Module Name’ If we removed the Student ID would we expect the module name to remain in our system? Yes or No?

26. Example 1 – 2NF Student ID Module Code Module Name Grade Examine the attribute ‘Module Name’ If we removed the Student ID would we expect the module name to remain in our system? Yes

27. Example 1 – 2NF Student ID Module Code Module Name Grade Examine the attribute ‘Module Name’ This tells us that Module Name IS NOT dependent on StudentID

28. Example 1 – 2NF Student ID Module Code Module Name Grade Examine the attribute ‘Module Name’ If we removed the Module Code would we expect the module name to remain in our system? Yes or No

29. Example 1 – 2NF Student ID Module Code Module Name Grade Examine the attribute ‘Module Name’ If we removed the Module Code would we expect the module name to remain in our system? No

30. Example 1 – 2NF Student ID Module Code Module Name Grade Examine the attribute ‘Module Name’ This tells us that Module Name IS dependent on Module Code

31. Example 1 – 2NF Student ID Module Code –Module Name Grade Examine the attribute ‘Module Name’ Module name is therefore dependant on only PART of the primary key This is called a partial dependency and must be removed

32. Example 1 – 2NF Student ID Module Code –Module Name Grade Examine the attribute ‘Grade’ Is it dependent on Student ID? Is it dependent on Module Code?

33. Example 1 – 2NF Student ID Module Code –Module Name Grade Examine the attribute ‘Grade’ Is it dependent on Student ID? Yes Is it dependent on Module Code?

34. Example 1 – 2NF Student ID Module Code –Module Name Grade Examine the attribute ‘Grade’ Is it dependent on Student ID? Yes Is it dependent on Module Code? Yes

35. Example 1 – 2NF Student ID Module Code –Module Name Grade Examine the attribute ‘Grade’ There is no partial dependency so it stays in this table

36. Example 1 – 2NF Student ID Module Code –Module Name Grade Module Name must be removed

37. Example 1 – 2NF Student ID Module Code Grade Module Name Module Name must be removed

38. Example 1 – 2NF Student ID Module Code Grade Module Code Module Name Module Name must be removed We need to give it a primary key This will be the part of the key on which it is dependent The data is now in 2NF

39. Example 1 – 2NF Student ID Student Name Course Course ID Student ID Module Code Grade Module Code Module Name

40. Example 2 Student ID Name Faculty Student ID Book ID Title Author Return Date Take this to 2NF

41. Example 2 - 2NF Student ID Name Faculty Student ID Book ID Return Date Book ID Title Author

42. Example 3 Customer ID Customer Name Address Branch No Branch Manager Customer ID Stock ID Title Format Take this to 2NF

43. Example 3 - 2NF Customer ID Customer Name Address Branch No Branch Manager Customer ID Stock ID Title Format

44. Example 1 - Anomalies There are still problems with Example 1 Insert –Still cannot add a course unless there are students taking it Update –Cannot update course name without finding all students on the course Delete –If we delete a student then we could also lose course information

45. Third Normal Form Applies to all tables Data in a table must depend on Nothing but the Key We must remove any non-key dependencies

46. Example 1 – 3NF Student ID Student Name Course Course ID Student ID Module Code Grade Module Code Module Name

47. Example 1 – 3NF Student ID Student Name Course Course ID Problems all seem to affect Course Data Student ID Module Code Grade Module Code Module Name

48. Example 1 – 3NF Student ID Student Name Course Course ID Examine the attribute “Student Name” If we removed the Student ID would we expect the Student Name to remain in our system?

49. Example 1 – 3NF Student ID Student Name Course Course ID Examine the attribute “Student Name” If we removed the Student ID would we expect the Student Name to remain in our system? No

50. Example 1 – 3NF Student ID Student Name Course Course ID Examine the attribute “Student Name” Therefore “Student Name” is dependent on Student ID and is in the correct table

51. Example 1 – 3NF Student ID Student Name Course Course ID Examine the attribute “Course”, which is the name of a course If we removed the Student ID would we expect the Course to remain in our system?

52. Example 1 – 3NF Student ID Student Name Course Course ID Examine the attribute “Course”, which is the name of a course If we removed the Student ID would we expect the Course to remain in our system? Yes

53. Example 1 – 3NF Student ID Student Name Course Course ID Examine the attribute “Course” Therefore “Course” IS NOT dependent on Student ID and must be moved

54. Example 1 – 3NF Student ID Student Name Course ID Course Examine the attribute “Course” The new table needs an appropriate Primary Key CourseID is the logical option

55. Example 1 – 3NF Student ID Student Name Course ID Course Examine the attribute “Course ID” If we removed the Student ID would we expect the student’s Course ID to remain in our system?

56. Example 1 – 3NF Student ID Student Name Course ID Course Examine the attribute “Course ID” Course ID is dependent on Student ID so must remain in the existing table Acts as a link between student and course

57. Example 1 – 3NF Student ID Student Name Course ID Course Examine the attribute “Course ID” If we removed the Student ID would we expect the student’s Course ID to remain in our system? No

58. Example 1 – 3NF Check the remaining tables to ensure they are in 3NF

59. Example 1 – 3NF Student ID Student Name Course ID Course Student ID Module Code Grade Module Code Module Name

60. Third Normal Form The Data is now in 3NF Data in a table must depend on –The Key –The Whole Key –And Nothing but the Key All Anomalies have now been removed

61. Example 2 - 2NF Student ID Name Faculty Student ID Book ID Return Date Book ID Title Author Take this to 3NF

62. Example 2 - 3NF Student ID Name Faculty Student ID Book ID Return Date Book ID Title Author Already in 3NF

63. Example 3 - 2NF Customer ID Customer Name Address Branch No Branch Manager Customer ID Stock ID Title Format Take this to 3NF

64. Example 3 - 3NF Customer ID Customer Name Address Branch No Branch Manager Customer ID Stock ID Title Format

65. References Whiteley, D. (2004) Introduction to Information Systems, Palgrave, 2004. Lejk, M. and D. Deeks (2002) Systems Analysis Techniques, Addison Wesley 2002 Mason, D. and L. Willcocks (1994), Systems Analysis, Systems Design, Alfred Waller, 1994.

66. References Yeates, D. and T. Wakefield (2004) Systems Analysis and Design, FT/Prentice Hall 2004 Gane, C. and T. Sarson (1979) Structured Systems Analysis, Prentice Hall, 1979 Eva, M (1994) SSADM Version 4: A users guide, McGraw hill, 1994

67. References DeMarco, T. (1979) Structured Analysis and System Specification, Yourdon, 1979 Royce, W. (1970) Managing the development of large software systems, In: Proceedings of IEEE WESCON, 1970 pp1-9. Connolly, T. and C. Begg (2000) Database Solutions, Addison-Wesley, 2000