Upload
milind-sonkamble
View
43
Download
2
Embed Size (px)
Citation preview
Database ConceptsDatabase Database ConceptsConcepts
Basic / Intermediate Basic / Intermediate
©Copyright 2004, Cognizant Academy, All Rights Reserved 2
About the Author
DBCONCEPT/PPT/1205/1.0Version:
Cognizant Academy Created By:
©Copyright 2004, Cognizant Academy, All Rights Reserved 3
Questions
A welcome Break
Coding Standards
Demo Key contacts
Reference
Test your understanding
Hands on exercise
Icons used
©Copyright 2004, Cognizant Academy, All Rights Reserved 4
Course Information
Basic and IntermediateLevel
Database ConceptsPrerequisites
This course covers all basic concepts that are required to understand the database concepts and normalization rules.
Course Description
©Copyright 2004, Cognizant Academy, All Rights Reserved 5
Module Outline
Module Flow:
1.Database Concepts
©Copyright 2004, Cognizant Academy, All Rights Reserved 6
Database Concepts: Overview
Introduction:Data is factual information, especially that is used for analysis or reasoning. Data on
its own has no meaning, but it becomes information when it is interpreted. Information is a collection of facts or data.
Objective:After completing this chapter, you will be able to:
Identify the purpose of a Database Management System (DBMS)Differentiate a field from a record and a column from a rowIdentify the basic components of an Entity-Relationship modelDefine the three types of relationships that can exist between entitiesExplain the purpose of normalizationDescribe the role of a primary key Explain the purpose of a foreign key Describe how to link data in different tables using a common fieldExplain the purpose of a Structured Query Language (SQL)
©Copyright 2004, Cognizant Academy, All Rights Reserved 7
Database Terminologies
Database– A logical structure to store data– An information set with a regular structure
Database Management System (DBMS)– A software used to create and interact with a database
©Copyright 2004, Cognizant Academy, All Rights Reserved 8
DBMS Components
The following are the components of a DBMS:
• Hardware
• Software
• Data
• Users
©Copyright 2004, Cognizant Academy, All Rights Reserved 9
Database Components
The components of a database are:
• Character
• Field
• Record
• File
©Copyright 2004, Cognizant Academy, All Rights Reserved 10
Components of a DBMS
A character:• Is the basic unit of data• Can be a letter, number, or special symbol
A field:• Is a group of related characters• Represents an attribute or characteristic of an entity• Corresponds to a column in a physical database
©Copyright 2004, Cognizant Academy, All Rights Reserved 11
Components of a DBMS (Contd.)
A record:• Is a collection of fields for one specific entity• Corresponds to a row in a physical database
The file is a group of records about the same type of entity.
©Copyright 2004, Cognizant Academy, All Rights Reserved 12
Sample Record
The figure displays how a customer’s information creates a data field and a record, and then becomes part of a file.
©Copyright 2004, Cognizant Academy, All Rights Reserved 13
DBMS Terminologies
Characters, fields, and files are terms applied to real-life characteristics (or old-fashioned systems). In database terms:– Characters are bytes of data– Fields are columns– Records are rows– Files are tables
DBMS terms used in the design and physical phase can be different.
©Copyright 2004, Cognizant Academy, All Rights Reserved 14
Review of Database Design
The database design has the following phases:
• Entity-Relationship Model (E-R Model)
• Normalization
©Copyright 2004, Cognizant Academy, All Rights Reserved 15
E-R Model
The following are the features of E-R Model: • E-R model is used to depict the relationship that exists among entities.• There are many variations of E-R modeling. Oracle teaches one version, other
vendors have slightly different graphical styles. However, most conform to the basics:– Entity– Cardinality– Optionality
©Copyright 2004, Cognizant Academy, All Rights Reserved 16
E-R Model Symbols
The figure shows E-R model notations.
©Copyright 2004, Cognizant Academy, All Rights Reserved 17
Relationships
The following relationships can be included in an E-R Model:
• One-to-one
• One-to-many
• Many-to-many
©Copyright 2004, Cognizant Academy, All Rights Reserved 18
One-to-one Relationship
Each occurrence (row) of data in one entity is related to only one occurrence of data in the other entity.
Example:
Each individual has just one Social Security Number (SSN), and each SSN is assigned to only one person.
©Copyright 2004, Cognizant Academy, All Rights Reserved 19
One-to-many Relationship
Each occurrence of data in one entity can be represented by many occurrences of the data in the other entity.
Example:
A class has only one instructor, but each instructor can teach many classes.
©Copyright 2004, Cognizant Academy, All Rights Reserved 20
Many-to-many Relationship
Data can have multiple occurrences in both entities.
Example:
A student can take many classes and each class is composed of many students.
©Copyright 2004, Cognizant Academy, All Rights Reserved 21
E-R Model: Example
The figure shows an E-R model for JustLee Books.
©Copyright 2004, Cognizant Academy, All Rights Reserved 22
Normalization
Normalization:
• Determines the required tables and columns for each table
• Is a multi-step process
• Is used to reduce or control data redundancy
• Results in a proper design of a database that can be easily modified without
restructuring the database
©Copyright 2004, Cognizant Academy, All Rights Reserved 23
First-Normal Form (1NF) and Primary Key
A table is in 1NF if:
– The primary key is identified
– Repeating columns are eliminated
Primary Key• Each row in a table must be able to be uniquely identified
• In any relational database, the ability to address specific rows in a table is
required
• A primary key is one or more columns that together uniquely identifies one row in
a table
©Copyright 2004, Cognizant Academy, All Rights Reserved 24
Second-Normal Form (2NF)
A table is in 2NF if:
• Subsets of data that apply to multiple rows of the table has been removed and
have been placed in separate tables.
• Relationship between the tables have been established using foreign keys.
©Copyright 2004, Cognizant Academy, All Rights Reserved 25
Third-Normal Form (3NF)
For a table to be in 3NF, all columns must be dependent on the full primary key:
– Any columns not related to the full primary key should be removed and if required, the columns should be converted to separate tables
– ‘Key’ for other tables are in the original table
©Copyright 2004, Cognizant Academy, All Rights Reserved 26
Summary of Normalization
• 1NF: Repeating groups have been eliminated and the primary key has been
identified
• 2NF: The table is in 1NF and partial dependencies have been eliminated
• 3NF: The table is in 2NF and transitive dependencies have been eliminated
©Copyright 2004, Cognizant Academy, All Rights Reserved 27
Linking Tables
Ensure the following when linking tables:
• Once tables are normalized, link certain tables
• Tables are linked through a common field
A common field is usually a primary key in one table and the foreign key in the other
table.
©Copyright 2004, Cognizant Academy, All Rights Reserved 28
Linking Tables
The figure shows JustLeeBook’s table structure after normalization.
©Copyright 2004, Cognizant Academy, All Rights Reserved 29
Structured Query Language (SQL)
Structured Query Language is:
• A data sub-language
• Used for:– Creating or modifying tables– Adding data to tables– Editing data in tables– Retrieving data from tables
©Copyright 2004, Cognizant Academy, All Rights Reserved 30
Structured Query Language (SQL)
SQL is composed of the following database languages:
1. Data Definition Language (DDL): SQL statements that are used to create or
destroy objects
2. Data Manipulation Language (DML): SQL statements that are used to query or
update data in tables
3. Data Control Language (DCL): SQL statements that are used to grant and
revoke privileges
©Copyright 2004, Cognizant Academy, All Rights Reserved 31
Allow time for questions from participants
©Copyright 2004, Cognizant Academy, All Rights Reserved 32
1. What is the difference between character, field, record and file? Give an example for each.
2. What is meant by data?3. What is the purpose of database? Give two examples?4. What is the difference between DBMS and RDBMS?5. Is Oracle a DBMS/RDBMS system?6. What is the full form of ERD?7. What is the difference between an entity and attribute?8. What are the different type of relationships you come across in an E/R model?9. Why a designer follows normalization during designing an application?10. What is meant by 1NF, 2NF, and 3NF? Give example for each?
Test Your Understanding
©Copyright 2004, Cognizant Academy, All Rights Reserved 33
Database Concepts: Summary
• The following are the components of a DBMS:– Hardware– Software– Data– Users
• The components of a database are:– Character– Field– Record– File
• Normalization: • Determines the required tables and columns for each table• Is a multi-step process• Is used to reduce or control data redundancy• Results in a proper design of a database that can be easily modified without
restructuring the database
©Copyright 2004, Cognizant Academy, All Rights Reserved 34
Database Concepts: Summary
The following relationships can be included in an E-R Model:
– One-to-one
– One-to-many
– Many-to-manyEnsure the following when linking tables:– Once tables are normalized, link certain tables– Tables are linked through a common field
Structured Query Language is:– A data sub-language – Used for:
→ Creating or modifying tables→ Adding data to tables→ Editing data in tables→ Retrieving data from tables
©Copyright 2004, Cognizant Academy, All Rights Reserved 35
Database Concepts: Next Step
The following items will provide more information on the subjects covered inthis Module:
Reference Topic or Module
DescriptionResource Type
http://www.learndatamodeling.com/URL
Database Concepts Absolute Beginner's Guide to Databases
Book
Disclaimer: Parts of the content of this course is based on the materials available from the Web sites and books listed above. The materials that can be accessed from linked sites are not maintained by Cognizant Academy and we are not responsible for the contents thereof. All trademarks, service marks, and trade names in this course are the marks of the respective owner(s).
Congratulations!You have successfully
completedDatabase Concepts
Congratulations!Congratulations!You have successfully You have successfully
completedcompletedDatabase ConceptsDatabase Concepts