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Database Systems Information Systems Intermediate 2.

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Presentation on theme: "Database Systems Information Systems Intermediate 2."— Presentation transcript:

1 Database Systems Information Systems Intermediate 2

2 Data and Information Data is raw, unprocessed facts and figures. Data is collected, stored and processed by computers. Examples: 368 HR101FE Baker 25168

3 Data and Information Information is processed data with structure or meaning. Information is useful to humans. Examples: Age: 36 years 8 months Post Code: HR10 1FE Date of Birth: 01/04/68 Occupation: Baker Total Spent: £251.68

4 What is a database? A database is a collection of related information about a set of persons or objects. Traditionally, databases have been manual paper based systems. Example: the Yellow Pages

5 What is a database management system? A database management system (DBMS) is a software package which is used to create, manipulate and present data from electronic databases. Example of DBMSs include Microsoft Access and Filemaker Pro.

6 Traditional databases storage of paper records was very bulky easy to mis-file a record, or records to be lost or damaged data often duplicated in several records keeping records up-to-date was difficult and time consuming, and often resulted in data inconsistency, where duplicated values were updated in one record but not in others many people employed to maintain the records, which was costly searching for records was time consuming producing reports, such as sorted lists or data collated from several sources, was extremely time consuming, if not impossible

7 Case Study: DVD Rentals Member NumberTitleForenameSurnameTelephone No. 1012MissIsobelRinger MrJohnSilver MrFredFlintstone MrsAnnetteKirton384756

8 Case Study: DVD Rentals DVD CodeTitleCostDate OutDate DueMember Number Name 002Finding Nemo£2.5003/09/0404/09/041034John Silver 003American Pie£2.5027/08/0428/08/041056F Flintstone 01/09/0402/09/04Isobel Ringer 008The Pianist£2.5004/09/0406/09/041097Annette Kirton 011Notting Hill£2.5027/08/0428/08/041012I Ringer 04/09/0406/09/041086F Flintstone 014Prime Suspect£2.0027/08/0428/08/04Annette Kirton 015Shrek£1.5010/09/0411/09/041034Joan Silver

9 Benefits of computerised databases Searching, sorting and calculating operations can be performed much more quickly and easily. Information is more easily available to users, due to improved methods of data retrieval. Data integrity is improved resulting in more accurate information.

10 Types of computerised database Flat file Relational

11 Flat file databases DVD CodeTitleCostDate OutDate Due Member NumberName Telephone Number 002Finding Nemo£2.5003/09/0404/09/041034John Silver American Pie£2.5027/08/0428/08/041056Fred Flintstone American Pie£2.5001/09/0402/09/041012Isobel Ringer The Pianist£2.5004/09/0406/09/041097Annette Kirton Notting Hill£2.5027/08/0428/08/041012Isobel Ringer Notting Hill£2.5004/09/0406/09/041056Fred Flintstone Prime Suspect£2.0027/08/0428/08/041097Annette Kirton Shrek£1.5010/09/0411/09/041034Joan Silver142536

12 Limitations of flat file databases Data is very likely to be duplicated. The duplication of data leads to the possibility of data inconsistency. It is not possible to store information about a member without entering details of a DVD. This is called an insertion anomaly. Removing a DVD from the database may remove the only record which stores details of a Member. This is called a deletion anomaly.

13 Relational databases A relational database stores data in more than one table. The idea is to ensure that data is only entered and stored once, so removing the possibility of data duplication and inconsistency.

14 Entities and Data Relationships An entity represents a person or object. e.g. Member, DVD Rental Each entity has a set of attributes which describe examples or instances of that entity. The attributes of the DVD Rental entity are code, title, cost, date out, date due and member number The attributes of the Member entity are member number, name and telephone number.

15 Entities, Attributes and Instances MEMBER Member NumberMember Name Telephone Number 1012Isobel Ringer John Silver Fred Flintstone Annette Kirton384756

16 Entities, Attributes and Instances The Member entity is the whole table MEMBER Member NumberMember Name Telephone Number 1012Isobel Ringer John Silver Fred Flintstone Annette Kirton384756

17 Entities, Attributes and Instances The Member entity is the whole table MEMBER Member NumberMember Name Telephone Number 1012Isobel Ringer John Silver Fred Flintstone Annette Kirton Each column stores one attribute, e.g. Member Name

18 Entities, Attributes and Instances The Member entity is the whole table MEMBER Member NumberMember Name Telephone Number 1012Isobel Ringer John Silver Fred Flintstone Annette Kirton Each column stores one attribute, e.g. Member Name Each row stores one instance, e.g. Member 1034

19 Entities, Attributes and Instances An entity represents a person or object. e.g. Member, DVD Rental Each entity has a set of attributes which describe examples or instances of that entity. The attributes of the DVD Rental entity are code, title, cost, date out, date due and member number The attributes of the Member entity are member number, name and telephone number.

20 Data Relationships Three types of relationship: One-to-one One-to-many Many-to-many

21 Data Relationships One-to-one

22 Data Relationships One-to-one One-to-many

23 Data Relationships One-to-one One-to-many Many-to-many

24 More than one table but theres a problem… DVD CodeTitleCostDate OutDate Due 002Finding Nemo£2.5003/09/0404/09/04 003American Pie 3£2.5001/09/0402/09/04 008The Pianist£2.5004/09/0406/09/04 011Notting Hill£2.5004/09/0406/09/04 014Prime Suspect£2.0027/08/0428/08/04 015Shrek£1.5010/09/0411/09/04 003American Pie 3£2.5027/08/0428/08/04 011Notting Hill£2.5027/08/9428/08/04 Member Number Member Name Telephone Number 1012Isobel Ringer John Silver Fred Flintstone Annette Kirton384756

25 More than one table DVD CodeTitleCostDate OutDate Due 002Finding Nemo£2.5003/09/0404/09/04 003American Pie 3£2.5001/09/0402/09/04 008The Pianist£2.5004/09/0406/09/04 011Notting Hill£2.5004/09/0406/09/04 014Prime Suspect£2.0027/08/0428/08/04 015Shrek£1.5010/09/0411/09/04 003American Pie 3£2.5027/08/0428/08/04 011Notting Hill£2.5027/08/9428/08/04 Member NumberMember NameTelephone NumberDVD Code 1012Isobel Ringer John Silver ? 1056Fred Flintstone Annette Kirton ?

26 More than one table DVD CodeTitleCostDate OutDate DueMember Number 002Finding Nemo£2.5003/09/0404/09/ American Pie 3£2.5001/09/0402/09/ The Pianist£2.5004/09/0406/09/ Notting Hill£2.5004/09/0406/09/ Prime Suspect£2.0027/08/0428/08/ Shrek£1.5010/09/0411/09/ Member NumberMember NameTelephone Number 1012Isobel Ringer John Silver Fred Flintstone Annette Kirton384756

27 Keys A key is a field, or set of fields, whose values uniquely identify a record. In any table, there may be more than one field, or set of fields, which can uniquely identify each recordthese are called candidate keys. The candidate key which is chosen to be used is called the primary key.

28 Keys Member NumberMember NameTelephone Number 1012Isobel Ringer John Silver Fred Flintstone Annette Kirton Member Number is a candidate key for the Member entity MEMBER(Member Number, Name, Telephone Number)

29 Keys DVD CodeTitleCostDate OutDate DueMember Number 002Finding Nemo£2.5003/09/0404/09/ American Pie 3£2.5001/09/0402/09/ The Pianist£2.5004/09/0406/09/ Notting Hill£2.5004/09/0406/09/ Prime Suspect£2.0027/08/0428/08/ Shrek£1.5010/09/0411/09/ DVD Code is a candidate key for the DVD Rental entity DVD RENTAL(DVD Code, Title, Cost, Date Out, Date Due, *Member Number) Member Number is called a foreign key.

30 Keys DVD CodeTitleCostDate OutDate DueMember Number 002Finding Nemo£2.5003/09/0404/09/ American Pie 3£2.5001/09/0402/09/ The Pianist£2.5004/09/0406/09/ Notting Hill£2.5004/09/0406/09/ Prime Suspect£2.0027/08/0428/08/ Shrek£1.5010/09/0411/09/ DVD Code is a candidate key for the DVD Rental entity DVD RENTAL(DVD Code, Title, Cost, Date Out, Date Due, *Member Number) Member Number is called a foreign key.

31 Keys A foreign key is a field which is not a primary key in its own table, but is a primary key in another table. Member Number is a foreign key in the DVD table, because it is the primary key in the Member table. Here is the data model: MEMBER(Member Number, Name, Telephone Number) DVD RENTAL(DVD Code, Title, Cost, Date Out, Date Due, *Member Number)

32 Implementation 3 steps: Set-up the tables Populate the tables Manipulate and present the data

33 Setting up the tables Which tables are required? Which fields are required? What are the properties of each field?

34 Setting up the tables Which tables are required? The tables correspond directly to the entities in the data model. In this case, there will be two tables, Member and DVD Rental.

35 Setting up the tables Which fields are required? The fields in each table are the attributes in each entity in the data model.

36 Setting up the tables What are the properties of each field? Its name be consistent!

37 Setting up the tables What are the properties of each field? Its name Its data type text numeric (integer, real, currency) date or time Boolean (yes or no) link object

38 Setting up the tables What are the properties of each field? Its name Its data type Validation: Presence check Restricted Choice check Range check

39 Populating the tables Take care to be accurate Validation: make sure the data is sensible Verification: make sure the date is correct Verification methods: Bar codes, OCR

40 Manipulating the Data Searching records Sorting records Calculating values Presenting results

41 Searching Which fields will be used to identify the records required? What are the search conditions for identifying the records required? Which fields will be displayed? E.g. Search for Test 3 = 10 Test 3 = 10 is called the search condition

42 Searching: Boolean operators OperatorMeaningExample = equal to Age = 16 Surname = Smith not equal to Height 1.70 Certificate PG > greater than or after Age > 17 Surname > N Date of Birth > 01/05/1952 < less than or before Height < 1.9 Surname < N Date of Birth < 31/06/1990 >= greater than or equal to or after and including Age >= 17 Postcode >= EH30 Date of Birth >= 01/05/1952 <= less than or equal to or before and including Height <= 1.95 Postcode <= EH20 Date of Birth <= 30/06/1990

43 Searching: wildcard characters

44 Character DescriptionExample * Matches any number of characters (zero or more). It can be used as the first or last character in the character string. wh* matches what, when, where, who, why, white, etc. ? Matches any single alphabetic character. b?ll matches ball, bell, bill and bull [ ] Matches any single character within the brackets. b[ae]ll matches ball and bell but not bill or bull ! Matches any character not in the brackets. b[!ae]ll matches bill and bull but not ball or bell – Matches any one of a range of characters. You must specify the range in ascending order (A to Z, not Z to A). b[a-c]d matches bad, bbd, and bcd # Matches any single numeric character. 1#3 matches 103, 113, 123, etc.

45 Wildcard Searches Search for Surname = *son

46 Complex Searches A complex search involves more than one search condition (and usually more than one field) Search for Test 3 = 10 AND Average > 6 Search for Test 3 = 10 OR Average > 6 Search for Test 3 > 5 AND Test 3 < 8 Search for Test 3 9

47 Sorting Which field will be used to decide the order of records? This is called the sort key. For the sort key, will the order of sorting be ascending or descending?

48 Sorting For a list of people with the tallest first sort in descending order of height For a list of people with youngest first sort in ascending order of age For alphabetical order sort in ascending order of surname ascending order of surname is called the sort condition

49 Complex Sorting A complex sort involves more than one sort condition involving two or more fields. The main sort key is called the primary sort key, and the second one is called the secondary sort key. Telephone book order: Ascending order of Surname, then Ascending order of Forename

50 Calculating Use formulas or expressions to calculate a value for a record based on other values in the record

51 Presenting Use Layouts (Filemaker Pro) Use forms and reports (Microsoft Access) Which fields are required? Perform a search and/or sorting operation and present the results


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