Database Management: Getting Data Together

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Database Management Getting Data Together

• Chapter 14

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Objectives

• Describe the hierarchy of data
• Explain the differences between files and
  databases
• List the four database models
• Describe the concept of data integrity
• Describe the functions of a database management
  system
• Describe the process of creating a database in
  general terms
• Compare and contrast relational and
  object-oriented databases
• Explain what a data warehouse is an how it
  differs from a database

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Contents

• Computer Databases
• Database Management Systems
• The DBMS Process
• Concurrency Control
• Security
• Backup and Recovery
• Looking at the Data

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Computer Databases

• Track information
• Keep consistent standards
• Allow higher productivity as a result of better
  information

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Hierarchy of Data

• Field
• Smallest meaningful unit of data
• Group of one or more characters that has a
  specific meaning
• Record
• Set of fields containing all information known
  about one entity
• Each record contains the same fields in the same
  sequence
• File
• Collection of related records

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Hierarchy of Data
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File Processing

• File processing
• Data redundancy
• Database models reduce redundancy
• Saves storage space
• Saves update effort
• Time
• Accuracy

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Database Models

• Database Types
• Relational
• Object-oriented
• Hierarchical
• Network
• Each type structures, organizes and uses data
  differently

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RDBMSRelational Database Management System

• Organizes data into related tables (files)
• Table consists of rows and columns
• Tables linked based upon a common field (key)

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RDBMSKey

• Primary key
• A field whose value uniquely identifies a record
• Foreign key
• Primary key of another table
• Used as link to other table
• May have duplicate values

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OODBMSObject-Oriented Database Management System

• Manipulates object-oriented databases
• Object represents a real-world entity
• Attributes / properties
• Data about the entity
• Methods / Actions
• Operations that work the data

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OODBMSObject-Oriented Database Management System

• Compared to RDBMS
• More complex
• Steeper learning curve
• Skilled employees needed who earn high pay
• Combined Object/relational DBMS
• Relational database that incorporates some
  complex data types

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Data Integrity

• Degree to which data is accurate and reliable
• Integrity constraints rules
• Acceptable values for a field
• Primary key values
• Foreign keys
• Integrity constraints must be enforced when data
  is entered or data is unreliable

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DBMSDatabase Management System

• Levels of software
• Sophisticated
• Mainframe
• Expensive tens of thousands of dollars
• Complex
• Planned and managed by computer professionals
• Simple
• PC
• Inexpensive few hundred dollars
• User can set up and use the database

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DBMSDatabase Management System

• Basic functions
• Create a database
• Enter data
• Modify the data as required
• Retrieve information from the database

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DBMSCreate a Database

• Data Dictionary / Catalog
• Stored data about the tables and fields within
  the database
• Per table
• Table name
• Relationships
• Per field
• Field name
• Data type
• Field size
• Validation rules

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DBMSEnter and Modify Data

• Operations
• Adding new data
• Modifying data
• Deleting data
• Methods
• User interacts directly with DBMS
• Programs written by professional programmers
  access the data using special commands built into
  the DBMS

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DBMSData Retrieval

• Extracting the desired data from the database
• Primary forms
• Queries
• Reports

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Query

• Ask a question about the data
• Present criteria that selects data from the
  database
• Results in smaller portion of the database
• Query Language
• Prepare your query using English-like statements
• Proprietary query language in DBMS

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Query

• SQLStructured Query Language
• Entered directly by user
• Included in programs

QBE Query-by-Example Graphical interface to
specify your criteria
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Report

• Formatted presentation of data from the database
• Normally printed
• Designed using a report generator

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The DBMS Process
Review the data and edit until accurate
Describe the data
Enter the data
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The DBMS Process
The Plan
The Report
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Concurrency Control

• Databases are used concurrently by many users
• Problem if several users attempt to update the
  same record at the same time
• Record locking
• First user requests record
• Others are locked out for update

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Concurrency Control
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Security

• Data is stored in a central location
• Problem unauthorized access is major concern
• Benefit easier to apply security measures
• Features
• User ID and password
• Privileges assigned to each user
• Read-only
• Update

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Backup and Recovery

• Why?
• Data can be accidentally damaged or destroyed
• Hardware can fail
• Forces of nature can cause physical damage
• Software or human errors can corrupt data
• Backup copy made periodically
• Recovery replaces the damaged database with the
  good backup

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Looking at the DataOLTP Online Transaction
Processing

• Supports day-to-day database activities
• Little support for data analysis

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Looking at the DataData Warehouses

• Databases designed to support ongoing operations
• Data is captured from the db
• Summary form
• Scheduled basis
• Period of time
• May include data from external sources

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Looking at the DataData Warehouses

• Online Analytical Processing (OLAP)
• Analyzes the data
• Produces information for managers
• Data mining
• Statistical and artificial intelligence
  techniques
• Look for unrecognized
• Patterns
• Relationships
• Correlations
• Trends
• Helps managers make strategic business decisions

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