Transcript Database Management: Getting Data Together

Database Management:
Getting Data Together
Chapter 14
Objectives
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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
RDBMS
Relational Database Management System
• Organizes data into related tables (files)
• Table consists of rows and columns
• Tables linked based upon a common
field (key)
RDBMS
Key
• 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
OODBMS
Object-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
OODBMS
Object-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
DBMS
Database Management System
Levels of software
• Sophisticated
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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
DBMS
Database Management System
Basic functions
• Create a database
• Enter data
• Modify the data as required
• Retrieve information from the database
DBMS
Create a Database
• Data Dictionary / Catalog
– Stored data about the tables and fields within the database
• Per table
– Table name
– Relationships
• Per field
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Field name
Data type
Field size
Validation rules
DBMS
Enter 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
DBMS
Data 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
SQL
Structured Query Language
Entered directly by user
Included in programs
QBE
Query-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
Describe the data
Review the data and
edit until accurate
Enter 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
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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 Data
OLTP – Online Transaction Processing
• Supports day-to-day database activities
• Little support for data analysis
Looking at the Data
Data 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 Data
Data Warehouses
• Online Analytical Processing (OLAP)
– Analyzes the data
– Produces information for managers
• Data mining
– Statistical and artificial intelligence techniques
– Look for unrecognized
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Patterns
Relationships
Correlations
Trends
– Helps managers make strategic business
decisions