Transcript Chapter 6 Assignment

Management Information Systems,
Sixth Edition
Chapter 6:
Databases and Data Warehouses
Objectives
• Explain the difference between traditional file
organization and the database approach to
managing digital data
• Explain how relational and object-oriented
database management systems are used to
construct databases, populate them with data,
and manipulate the data to produce information
• Enumerate the most important features and
operations of a relational database, the most
popular database model
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Objectives (continued)
• Understand how data modeling and design
creates a conceptual blueprint of a database
• Discuss how databases are used on the Web
• List the operations involved in transferring data
from transactional databases to data
warehouses
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Managing Digital Data
• Businesses collect and dissect data for many
purposes
• Data can be stored in database format
– Easy access and manipulation
• Databases have had a profound impact on
business
– An information industry has been created
• Database technology integrated with the Internet
has contributed to commerce significantly
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The Traditional File Approach
• Traditional file approach: no mechanism for
tagging, retrieving, or manipulating data
• Database approach: provides powerful
mechanism for managing and manipulating data
• Traditional approach is inconvenient:
– Program-data dependency
– High data redundancy
– Low data integrity
• Data redundancy: duplication of data
• Data integrity: accuracy of data
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The Traditional File Approach
(continued)
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The Database Approach
• Database approach: data organized as entities
• Entity: an object about which an organization
chooses to collect data, such as:
– People
– Events
– Products
• Character: smallest piece of data
– A single letter or a digit
• Field: single piece of information about entity
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The Database Approach (continued)
• Record: collection of related fields
• File: collection of related records
• Database fields can hold images, sounds, video
clips, etc.
• Field name allows easy access to the data
• Database management system (DBMS):
program used to:
– Build databases
– Populate a database with data
– Manipulate data in a database
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The Database Approach (continued)
• Query: a message to the database requesting
data from specific records and/or fields
• Database must be properly secured
– Not everyone should have access to all data
– Users will have different views of the database,
based on the data they are allowed to see
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The Database Approach (continued)
• Database administrator (DBA): the person
responsible for managing the database
– Sets user limits for access to data in the database
• DBMS is usually bundled with a programming
language
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Database Models
• Database model: general logical structure
– How records stored in the database
– How relationships between records are
established
• Database models differ in:
– How records are linked to each other
– How users can navigate the database, retrieve
records, and create records
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The Relational Model
• Relational Model: consists of tables
• Based on relational algebra
– Tuple: record (or row)
– Attribute: field (or column)
– Relation: table of records
• To design a relational database, you must
understand the entities to be stored in the
database and how they relate
• Tables are independent of each other, but can
be related to each other
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The Relational Model (continued)
• Key: a field whose values identify records
– Used to retrieve records
• Primary key: a field by which records are
uniquely identified
– Each record in the table must have a unique key
value
• Composite key: combination of fields that serve
as a primary key
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The Relational Model (continued)
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The Relational Model (continued)
• Foreign key: a field that is common to two tables
– Used to link the tables
– This field is a primary key in one table and a
foreign key in the other
• Join table: composite of tables
• Two types of table relationships:
– One-to-many relationship: one item in a table is
linked to many items in the other table
– Many-to-many relationship: many items in a
table are linked to many items of the other table
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The Object-Oriented Model
• Object-oriented database model: uses objectoriented approach for the database structure
• Encapsulation: combined storage of data and
relevant procedures to process it
– Allows object to be “planted” in different data sets
• Inheritance: the ability to create a new object by
replicating the characteristics of an existing
(parent) object
• Object-oriented databases (ODBs) store data
objects, not records
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Relational Operations
• Relational operation: creates a temporary
subset of a table or tables
• Used to create a limited list or a joined table list
• Three important relational operations:
– Select: a selection of records based on conditions
– Project: a selection of certain columns from a
table
– Join: join data from multiple tables to create a
temporary table
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Structured Query Language
• Structured Query Language (SQL): query
language of choice for DBMSs
• Advantages of SQL:
– It is an international standard
– It is provided with most relational DBMSs
– It has easy-to-remember, intuitive commands
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The Schema and Metadata
• Schema: a plan that describes the structure of
the database, including:
– Names and sizes of fields
– Identification of primary keys
– Relationships
• Data dictionary: a repository of information
about the data and its organization
– Also called metadata: the data about the data
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The Schema and Metadata (continued)
• Metadata includes:
–
–
–
–
–
Source of the data
Tables related to the data
Field and index information
Programs and processes that use the data
Population rules: what is inserted, or updated,
and how often
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Data Modeling
• Databases must be carefully planned and
designed to meet business goals
• Data modeling: analysis of an organization’s
data and identification of the data relationships
– A proactive process
– Develops a conceptual blueprint of the database
• Entity relationship diagram: a graphical
representation of all entity relationships
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Data Modeling (continued)
• Entity relationship diagram is composed of:
–
–
–
–
–
Boxes: identify entities
Lines: indicate relationship between entities
Crossbars: indicate mandatory fields
Circles: indicate optional
Crow’s feet: identify “many”
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Data Modeling (continued)
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Data Modeling (continued)
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Databases on the Web
• Web is dependent on databases
– Organizations must link their databases to the
Web
• Interface between Web and database required
• Interface may be programmed in one of several
Web programming languages, including:
–
–
–
–
Java servlets
Active server pages (ASP)
PHP (Hypertext Preprocessor)
Web application program interfaces (APIs)
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Databases on the Web (continued)
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Data Warehousing
• Most data collections are used for transactions
• Accumulation of transaction data is useful
• Data warehouse: a large repository database
that supports management decision making
– Typically relational
– Data is collected from transactional databases
• Data mart: a smaller collection of data focusing
on a particular subject or department
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From Database to Data Warehouse
• Transactional databases are not suitable for
business analysis
– Contain only current, not historical data
• Data warehouse requires large storage capacity:
– Mainframe computers are often used
– Scalability is an issue
– Data warehouses grow continually
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Phases in Data Warehousing
• Three phases in transferring data from a
transactional database to a data warehouse:
– Extraction phase: create files from transactional
database
– Transformation phase: cleanse and modify the
data format
– Loading phase: transfer files to data warehouse
• A properly built data warehouse becomes a single
source for all data required for analysis
• Data mining and online analytical processing
(OLAP) use data in data warehouses
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Summary
• Organizations collect vast amounts of data
• Database approach has several advantages
over traditional file approach
• Character: smallest piece of data
• Field: made up of multiple characters
• Record: collection of related fields
• File: collection of related records
• Database management system (DBMS): tool to
construct databases
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Summary (continued)
• Relational and object-oriented database models
have different advantages
• Keys are used to form links among entities
• Primary keys are unique identifiers
• Object-oriented database maintains objects that
contain data and procedures that process it
• Structured Query Language (SQL) is an
international standard for querying databases
• Database designer must construct a schema to
construct a database
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Summary (continued)
• Database designers conduct data modeling and
create entity relationship diagrams to plan
databases
• Many databases are linked to Web
• Data warehouses contain huge collections of
historical transaction data
• Data warehouse requires data extraction,
transformation, and loading of transactional data
• Invasion of privacy is exacerbated by database
technology
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