Introduction to Databases: Understanding Data and Information

1. Introduction to Data Bases

2. 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

3. 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

4. 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

5. 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

6. 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

7. Other Terms (cont.) • Types of Data • Text: Sorts/Queries based on ASCII values of characters

8. ASCII Table

9. 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

10. 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

11. 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

12. A Table: where you are looking

13. A Criteria: what you want

14. A Report: how you want it to look