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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

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data networks

Data & Networks

Problem Solving with Computers

data information
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
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?
questions queries1
Questions & Queries
  • Database
    • Data organized to facilitate information retrieval
  • Query
    • A question we ask of the database
questions queries2
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
Objects & Attributes
  • An object is a “thing” we wish to work with, such as …
    • Person
    • Sales receipt
    • Car
    • Music CD
objects attributes1
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 attributes2
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
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
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
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
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?
tables1

Field

Record

Tables

Used Cars

try this
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 this1
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
Database Management Software
  • Used to create and edit databases
    • Examples:
      • Microsoft Access
      • Filemaker Pro
  • Facilitates
    • Creation of tables
    • Data entry
    • Data retrieval
exercise
Exercise
  • Use Microsoft Access to implement your database design for college course sections
relationships
Relationships
  • Associations between two tables
  • Based on common field(s)
  • Often used to reduce errors and/or duplication of data
example car dealership database
Example:Car Dealership Database
  • Tables
    • Car Models
    • Cars

Models

Cars

example car dealership database1
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 database2
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 database3
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 database4
Example:Car Dealership Database

Models

Cars

Do this for homework!

queries
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?
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