acis notes for test 3

acis notes for test 3 - Click to edit Master subtitle style...

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Unformatted text preview: Click to edit Master subtitle style 9/1/10 Chapter 5 Database Processing 9/1/10 Objectives  Define database.  Understand the advantages of using databases.  Know when to implement a database. 9/1/10 How Google Works  Web Crawler  Indexer  Query Processor 9/1/10 Google’s Web Crawler › Finds pages on the web and gives full text of pages to Indexer › Extracts links from new pages for subsequent crawling 9/1/10 Google’s Indexer  Each significant word in page is extracted and indexed  Results stored in tables: › Search term › URL of page containing term › Location of term on page › Number of times term appears on page 9/1/10 Google’s Query Processor  User Interface – allows you to identify search criteria  Engine – matches search criteria to index of terms previously stored  Results Formatter › displays URLs containing search terms › displayed in order by a ranking that is based on other data stored about the term’s appearance 9/1/10 The Google Process From: googleguide.com/google_works.html 9/1/10 Purpose of a Database Keep track of data with multiple themes 9/1/10 What is a Database? • Collections of records • Related tables • Metadata 9/1/10 Metadata Customer Table  Cust ID – 3 numeric digits, must be unique  First Name – up to 20 alphanumeric digits, required  Last Name – up to 25 alphanumeric digits, required 9/1/10 Database Benefits  ad-hoc information retrieval  only relevant data is output  shared access  security  data integrity  referential integrity can be enforced automatically  data independence 9/1/10 Data Anomaly Database Vocabulary  Database  Table or Entity  Record  Field or Attribute  Value 9/1/10 Key Attributes  Primary Key – uniquely identifies each row/record in a table  Foreign Key – connects a row in one table with one or more rows in another 9/1/10 Self Check Question  The structure and organization of the database is described by its: A. attribute B. value C. metadata D. property 9/1/10 E-R Model Logical representation of database 9/1/10 Relationships  A Customer may have a minimum of zero and a maximum of many Orders.  An Order may belong to a minimum of one and a maximum of one Customer. Cus t ID- PK F irs t Name Las t Name E-ma il Cus tomer O rder #- PK Cus t ID- FK Da te To ta l Amoun t O rder m in imum max imum 9/1/10 Self Check Question  A small health food store has customers that pay a one-time membership fee. These members receive reduced prices on all merchandise. A list of all customers who have paid this one-time fee (showing...
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This note was uploaded on 08/31/2010 for the course ACIS 1504 taught by Professor Jmlacoste during the Fall '07 term at Virginia Tech.

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acis notes for test 3 - Click to edit Master subtitle style...

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