Data &amp; Networks

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# Data & Networks - PowerPoint PPT Presentation

Data &amp; Networks. Problem Solving with Computers. Data &amp; Information. Data is facts and figures Information is presented data But, before we extract information from data … Data often needs to be organized. Questions &amp; Queries. We often ask questions to obtain information

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### Data & Networks

Problem Solving with Computers

Data & Information
• Data is facts and figures
• Information is presented data
• But, before we extract information from data …
• Data often needs to be organized
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
Questions & Queries
• Database
• Data organized to facilitate information retrieval
• Query
• A question we ask of the database
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?
Objects & Attributes
• An object is a “thing” we wish to work with, such as …
• Person
• Sales receipt
• Car
• Music CD
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
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
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
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

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
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?

Field

Record

Tables

Used Cars

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
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?
Database Management Software
• Used to create and edit databases
• Examples:
• Microsoft Access
• Filemaker Pro
• Facilitates
• Creation of tables
• Data entry
• Data retrieval
Exercise
Relationships
• Associations between two tables
• Based on common field(s)
• Often used to reduce errors and/or duplication of data
Example:Car Dealership Database
• Tables
• Car Models
• Cars

Models

Cars

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

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

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

Example:Car Dealership Database

Models

Cars

Do this for homework!

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?