CHAPTER 6 DATABASES

CHAPTER 6 DATABASES

1. - Collection of data organized so you can access, retrieve and use it

   • - Software allows you to create database, add change and delete data, sort and retrieve data

2. (1) Data and Information

   • DATA: a collection of unprocessed items
     • INFORMATION: data that is organized and meaningful
       • DATA INTEGRITY: degree to which data is correct
         • Garbage in, garbage out (GIGO) computer phrase that means you cannot create correct information from incorrect data

3. (2) Hierachy of Data

   • - Database contains files, file contains records, record contains fields, filed contains characters
     • FIELD
       • - Combination of one or more characters
         • Field Name: uniquely identifies each field
           • Field Size: defines the max num of characters a field can contain
             • Data Type: specifies kind of data field contains
     • Common Data Type
       • Text, Numeric, AutoNum, Currency, Date, Memo, Yes/No, Hyperlink, Object
     • Record
       • - Group of related fields
         • - Key field, or primary key, uniquely identifies each record
     • Data File
       • - Collection of related records stored on disk

4. (3) Maintaining Data

   • VALIDATION: process of comparing data with a set of ruled to find out if data is correct
     • Types of validity checks: Check Digit, Alphabetic/Numeric Check, Completeness Check, Range Check, Consistency Check
   • FILE MAINTENANCE: procedures that keep data current
     • Adding records
     • Changing records
     • Deleting records

5. (4) File Processing Vs Databases

   • FILE PROCESSING SYSTEM
     • - Each department or area within organization has own set of files
       • - Records in one file mayu not relate to records in any other file
         • Weaknesses
           • Data redundancy - some fields stored in multiple files
           • Isolated data - data stored in separate files so it is difficult to access
   • DATABASE APPROACH
     • - Many programs and users can share data in database
       • - Secures data so only authorized users can access certain data
         • How processing application ?
           • Strengths
             • Reduced data redundancy
             • Improved data integrity
             • Shared data
             • Easier access
             • Reduced development time

6. (5) Database Management Systems

   • DATA DICTIONARY: contains data about each file in database and each field within those files
     • DATA SECURITY: to ensure only authorized users can access data
       • Read-only privileges - user can view data, but connot change it
       • Full-update privileges - user can view and change data
       • BACKUP: a copy of the entire database
         • LOG: a listing of activities that change database contents
           • RECOVERY UTILITY: users logs/backups to restore database when it is damaged/destroyed
             • Rollforward (Forward Recovery): uses log to re-enter changes made to database since last save/backup
             • Rollback (Backward Recovery): uses log to undo any changes made to database during a certain period of time
             • Structured Query Language (SQL): allows u to manage, update and retrieve data

7. (6) Data Warehouse

   • - Huge database system that stores and manages data required to analyze historical and current transactions
     • - Quick and efficient way to access large amounts of data
       • - Often uses a process called data mining to find patterns and relationships among data
         • - Uses multidimendional databases
           • - Data mart is smaller version of data warehouse

8. (7) Web Database

   • - Database u access through the Web by filling in a form on a Web page
     • - Usually resides on a database server, a computer that stores and provides access to a database

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