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Learn about the fundamentals of data and information, including how data is processed, categorized, and used in databases. Explore key concepts such as entities, facts, levels of data, types of data, and the relational model.
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What is (are) Data • Information? - no • Information is PROCESSED data • Data are facts - descriptions of an entity, • Entity -> Me • Facts -> Name, Address, Phone, Age, Ht, Wt, IQ, Eye, Hair • Facts can be related or unrelated • Name -> First, Last, MI • Address -> Str#, Street, City, State, Zip
Data (cont.) • Facts can be Unique to an entity (SSAN) • Facts can group people (City, Zip, Eye Color, Income) • Facts give information, but must be processed • - Relate to an entity: SSAN->Individual • - Counted: Population of a state • - Ordered: Names in a telephone book • - Searched: Finding the people on a street with children • - Segregated: Finding registered voters in a district
Levels of Data • Bit - 1's & 0's, Computers think in it • Character - One or more Bits • Field - One or more Characters, max size important • Record - One or more Fields, Single field data file is a list • File - One or more Records, (Draw flat file example) (N, SS#, Ph) • (Note) Here is where most folks stop
Data Base - One or more files - Why more than one file? • Different sources List of names and address of students - List of Grades from each class - Merged to form ...Report Cards • Info not achievable otherwise - List of names & Defaulted Loans - List of voter registrations - Result is recovery of money
Other Terms • Data Banks: Groups of Data Bases • DBMS: Data Base Management System • Keys: The order that records are sorted/searched. Can be more than one • Primary Key: Should be unique to each record • Secondary Key(s) • Compound Keys: Eg. LName FName MI
Other Terms (cont.) • Types of Data • Text: Sorts/Queries based on ASCII values of characters
Other Terms (cont.) • Types of Data • Text: Sorts/Queries based on ASCII values of characters • Number: Math functions can be performed on these values • Date: Based on number of days since 12/31/1899 • Days can be added or subtracted forming new dates (Eg: 01/01/2006 + 7 = 01/08/2006) • DBMS: Data Base Management System
The Relational Model • Data is stored on “Tables” of fixed-length records • Portions of records called “Fields” • Similar fields in different files can be “Related” • Individual records in different files can be linked based on data in “Related” fields being identical • Very Flexible, Relations created “On-The-Fly” • Makes Cross-referencing possible Tickets Issued Driver’s Licences Tic# Date DL# DL# Name Address 10101 1/1/97 60123 60123 Doe 151 Main
Other Terms (cont.) • Queries • Method for selecting records that fit a criteria given • Eg: List all the records where the Last Name begins with the letter S • In MS Access • LName (assuming that’s what you named the field) in the Field Box • “S*” in the Criteria Box • “*S*” for a sliding match (field contains the letter S) • Queries Need three elements