Database Management: Getting Data Together

Chapter 14

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

Contents

• Computer Databases

• Database Management Systems

• The DBMS Process

• Concurrency Control

• Security

• Backup and Recovery

• Looking at the Data

Computer Databases

• Track information

• Keep consistent standards

• Allow higher productivity as a result of better information

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

Hierarchy of Data

File Processing

• File processing– Data redundancy

• Database models reduce redundancy– Saves storage space– Saves update effort

• Time• Accuracy

Database Models

• Database Types– Relational– Object-oriented– Hierarchical– Network

• Each type structures, organizes and uses data differently

RDBMSRelational Database Management System

• Organizes data into related tables (files)

• Table consists of rows and columns

• Tables linked based upon a common field (key)

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

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

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

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

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

DBMSDatabase Management System

Basic functions

• Create a database

• Enter data

• Modify the data as required

• Retrieve information from the database

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

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

DBMSData Retrieval

• Extracting the desired data from the database

• Primary forms– Queries– Reports

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

Query

SQLStructured Query Language

Entered directly by userIncluded in programs

QBEQuery-by-Example

Graphical interface to specify your criteria

Report

• Formatted presentation of data from the database

• Normally printed

• Designed using a report generator

The DBMS Process

Enter the data

Review the data and edit until accurateDescribe the data

The DBMS Process

The Plan…

The Report…

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

Concurrency Control

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

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

Looking at the DataOLTP – Online Transaction Processing

• Supports day-to-day database activities

• Little support for data analysis

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

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