Data & Networks

1. Data & Networks Problem Solving with Computers

2. Data & Information • Data is facts and figures • Information is presented data • But, before we extract information from data … • Data often needs to be organized

3. Questions & Queries • We often ask questions to obtain information • The data we receive is organized such that we can readily see it’s information content • What about computers?

4. Questions & Queries • Database • Data organized to facilitate information retrieval • Query • A question we ask of the database

5. Questions & Queries • What data would you need to answer the following questions? • What percentage of students at WCSU have at least a 3.0 GPA? • How many students graduated for each of the past five years?

6. Objects & Attributes • An object is a “thing” we wish to work with, such as … • Person • Sales receipt • Car • Music CD

7. Objects & Attributes • Objects in a collection share common attributes with each other • Example: • Objects: Cars • Attributes: Make, Model, Year, Color, Price, etc. • Attributes yield a method for describing an object, but are not the final object description

8. Objects & Attributes • Problem • Develop a set of six (6) attributes for describing college students • Remember, the actual set of values for these attributes should be unique for each student

9. Fields & Records • Each object in a collection is represented by a record in a database • Each attribute identified for the collection is represented by a one or more fields

10. Database Collection • A database is a collection of records Object • To be useful, there should be a one-to-one correspondence between objects and records Record Database

11. Models • Therefore … • A record is a model for an object • A database is a model for a collection of objects • A database can consist of one or more database files

12. Tables • Databases are often stored as tables • Each row in a table is a record • Each column in a table is a field • Each field has an associated datatype and perhaps a length • Hmmm … almost sounds like fields are variables, eh?

13. Field Record Tables Used Cars

14. Try this! • Problem: • Create a simple table design for college course sections • Select attributes that will yield a unique record for each course section • Work in pairs • You have 15 minutes to complete this exercise

15. Try this! • Primary key • One or fields that represent a unique set of data for each record • How did you insure that each record was unique? • Was there any duplicate data?

16. Database Management Software • Used to create and edit databases • Examples: • Microsoft Access • Filemaker Pro • Facilitates • Creation of tables • Data entry • Data retrieval

17. Microsoft Access Demo

18. Exercise • Use Microsoft Access to implement your database design for college course sections

19. Relationships • Associations between two tables • Based on common field(s) • Often used to reduce errors and/or duplication of data

20. Example:Car Dealership Database • Tables • Car Models • Cars Models Cars

21. Example:Car Dealership Database • Each car can be associated with one model • Each model can be associated with many cars • This is a one-to-many relationship Models 1 Cars n

22. Example:Car Dealership Database • Sometimes, a record in one related file cannot exist without a record in another file • Is that the case here? • Can you imagine a situation where this was true? Models 1 Cars n

23. Example:Car Dealership Database • A common field(s) is required to form the link between two related files Models Model ID : 1 Cars Model ID : n

24. Example:Car Dealership Database Models Cars Do this for homework!

25. Queries • A structured question “asked” of a database • Examples: • How many cars were sold in January? • What cars were sold in January? • Were any cars sold in March? • What is the data type for each answer?

26. Networks