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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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