Databases
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Transcript of Databases
Databases
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IntroductionDatabase: an organized collection of dataDatabase management system (DBMS):
group of programs to manage databaseManipulates databaseProvides an interface between database and
the user of the database and other application programs
Database administrator (DBA): skilled IS professional who directs all activities related to an organization’s database
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Add, change,
and delete data
Add, change,
and delete data
CreatedatabaseCreate
database
Sort and
retrieve data
Sort and
retrieve data
Createforms and
reports
Createforms and
reports
Data and Information
Database software allows you to
Database software allows you to
Collection of data organized so
you can access, retrieve, and
use it
Collection of data organized so
you can access, retrieve, and
use it
Database software also called database management system
(DBMS)
Database software also called database management system
(DBMS)
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The Database Approach“Traditional” (ie-OLD) approach to database
management: separate data files are created for each applicationResults in data redundancy (duplication)Data redundancy conflicts with data integrity
Database approach to database management: pool of related data is shared by multiple applicationsSignificant advantages over traditional
approach
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Isolated data—data stored
in separate files so it is difficult to
access
Isolated data—data stored
in separate files so it is difficult to
access
File Processing System
Data redundancy—
same fields stored in
multiple files
Data redundancy—
same fields stored in
multiple files
Each department or
area within organization
has own set of files
Each department or
area within organization
has own set of files
May have weaknessesMay have
weaknesses
Records in one file may not relate to
records in any other file
Records in one file may not relate to
records in any other file
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Strengths of the database approach
Reduced data
redundancy
Reduced data
redundancy Improved data
integrity
Improved data
integrityShared
dataShared
dataEasier access
Easier access
Reduced development
time
Reduced development
time
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The Hierarchy of DataField: typically a name, number, or
combination of characters that describes an aspect of a business object or activity
Record: a collection of related data fieldsFile: a collection of related recordsDatabase: a collection of integrated and
related files
Hierarchy of data: Fields records files
databases
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Relational DatabasesMS-Access is an example of a relational
database
Some terminology differences in relational databases:
Record equates to a RowField equates to a Column
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File KeysKey: field or set of fields in a record that is
used to identify the recordPrimary key: field or set of fields that
uniquely identifies the record
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3. Design the records and fields for each table
2. Design the tables
1. Determine the purpose of the database1. Determine the purpose of the database
4. Determine the relationships among the tables
4. Determine the relationships among the tables
Design tables on paper first Each table should contain
data about one subject
Database Administration
Be sure every record has a unique primary key
Use separate fields for logically distinct items
Do not create fields for information that can be derived from entries in other fields
Allow enough space for each field Set default values for frequently
entered data
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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
Garbage out
Garbage in
Data integrity is lost
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UsefulUsefulAccessibleAccessible
OrganizedOrganized
Qualities of Valuable Information
TimelyTimely
VerifiableVerifiable
AccurateAccurate
Cost-effectiveCost-effective
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Manipulating Data and Generating ReportsQuery-By-Example (QBE): a visual
approach to developing database queries or requests
Structured Query Language (SQL): standard query language for relational databases
Database programs can produce reports, documents, and other outputs
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Queries Request for specific data from a
database Query language consists of simple,
English-like statements that allow users to specify data to display, print, or store
Step 1. Select the fields you want to display in the resulting query.
Step 2. Assign a name to the query, so you can open it later.
Step 3. View query on the screen.
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Structured Query Language (SQL)?• Allows you to manage, update, and retrieve data
• Has special keywords and rules included in SQL statements
SQL statement
SQL statement results
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Database Security
Read-only privileges -
user can view data, but cannot change it
Read-only privileges -
user can view data, but cannot change it
DBMS provides means to ensure only authorized users can access
data
DBMS provides means to ensure only authorized users can access
data
Access privileges
define activities that specific user or group of users
can perform
Access privileges
define activities that specific user or group of users
can perform
Full-update privileges -
user can view and
change data
Full-update privileges -
user can view and
change data
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Data Warehouse/Data Mining/Data Mart
Data mart is smaller version of data warehouse
Uses multidimensional databases
Often uses a process called data mining to find patterns and relationships among data
Data warehouse: database system that stores and manages data required to analyze historical and current transactions
Quick and efficient way to access large amounts of data
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Quote
Alice came to a fork in the road. "Which road do I take?" she asked.
"Where do you want to go?" responded the Cheshire cat.
"I don't know," Alice answered.
"Then," said the cat, "it doesn't matter.“
~Lewis Carroll, Alice in Wonderland