This document provides an overview of key concepts in database management systems including data models, normalization, and relational algebra. It defines entities, attributes, and relationships in an entity-relationship model and tables, tuples, and keys in a relational model. The document also discusses normalization techniques like 1NF, 2NF, and 3NF to reduce data anomalies and improve database design. Relational algebra operations like select, project, join, and union are introduced as a procedural query language to retrieve and manipulate data from relational databases.
2. INTRODUCTION
• DATA: RAW FACTS
• INFORMATION:PROCESSED DATA
• DATABASE: COLLECTION OF INTERRELATED DATA
• DBMS:SOFTWARE THAT MANAGES THE DATABASE
• DBMS SOFTWARES: MYSQL,ORACLE ,POSTGRES, SQLSERVER, DB2,
SQLITE,MONGODB
• SCHEMA: A DATABASE SCHEMA IS THE SKELETON STRUCTURE THAT REPRESENTS THE LOGICAL VIEW OF THE ENTIRE DATABASE. IT
DEFINES HOW THE DATA IS ORGANIZED AND HOW THE RELATIONS AMONG THEM ARE ASSOCIATED. IT FORMULATES ALL THE CONSTRAINTS THAT
ARE TO BE APPLIED ON THE DATA.
• INSTANCE:THE DATA STORED IN DATABASE AT A PARTICULAR MOMENT OF TIME IS CALLED INSTANCE OF DATABASE.
• DBA:DATABASE ADMINISTRATOR
5. ER MODEL
• ENTITY RELATIONSHIP MODEL
• 1. ENTITY
AN ENTITY IS AN OBJECT OR COMPONENT OF DATA. AN ENTITY IS REPRESENTED AS
RECTANGLE IN AN ER DIAGRAM.
• 2. ATTRIBUTE
AN ATTRIBUTE DESCRIBES THE PROPERTY OF AN ENTITY. AN ATTRIBUTE IS REPRESENTED AS
OVAL IN AN ER DIAGRAM. THERE ARE FOUR TYPES OF ATTRIBUTES:
• 1. KEY ATTRIBUTE
2. COMPOSITE ATTRIBUTE
3. MULTIVALUED ATTRIBUTE
4. DERIVED ATTRIBUTE
7. 3. Relationship
A relationship is represented by diamond shape in ER diagram, it shows the relationship among entities.
There are four types of relationships:
1. One to One
2. One to Many
3. Many to One
4. Many to Many
9. RELATIONAL MODEL
• THE RELATIONAL MODEL REPRESENTS THE DATABASE AS A COLLECTION OF RELATIONS. A RELATION IS A TABLE OF VALUES.
• ATTRIBUTE: EACH COLUMN IN A TABLE. ATTRIBUTES ARE THE PROPERTIES WHICH DEFINE A RELATION. E.G., STUDENT_ROLLNO,
NAME,ETC.
• TABLES – IN THE RELATIONAL MODEL THE, RELATIONS ARE SAVED IN THE TABLE FORMAT. IT IS STORED ALONG WITH ITS ENTITIES. A
TABLE HAS TWO PROPERTIES ROWS AND COLUMNS. ROWS REPRESENT RECORDS AND COLUMNS REPRESENT ATTRIBUTES.
• TUPLE – IT IS NOTHING BUT A SINGLE ROW OF A TABLE, WHICH CONTAINS A SINGLE RECORD.
• RELATION SCHEMA: A RELATION SCHEMA REPRESENTS THE NAME OF THE RELATION WITH ITS ATTRIBUTES.
• DEGREE: THE TOTAL NUMBER OF ATTRIBUTES WHICH IN THE RELATION IS CALLED THE DEGREE OF THE RELATION.
• CARDINALITY: TOTAL NUMBER OF ROWS PRESENT IN THE TABLE.
• COLUMN: THE COLUMN REPRESENTS THE SET OF VALUES FOR A SPECIFIC ATTRIBUTE.
• RELATION INSTANCE – RELATION INSTANCE IS A FINITE SET OF TUPLES IN THE RDBMS SYSTEM. RELATION INSTANCES NEVER HAVE
DUPLICATE TUPLES.
• RELATION KEY - EVERY ROW HAS ONE, TWO OR MULTIPLE ATTRIBUTES, WHICH IS CALLED RELATION KEY.
• ATTRIBUTE DOMAIN – EVERY ATTRIBUTE HAS SOME PRE-DEFINED VALUE AND SCOPE WHICH IS KNOWN AS ATTRIBUTE DOMAIN
11. RELATIONAL INTEGRITY CONSTRAINTS
RELATIONAL INTEGRITY CONSTRAINTS IS REFERRED TO CONDITIONS WHICH
MUST BE PRESENT FOR A VALID RELATION. THESE INTEGRITY CONSTRAINTS ARE
DERIVED FROM THE RULES IN THE MINI-WORLD THAT THE DATABASE
REPRESENTS.
• DOMAIN CONSTRAINTS
• KEY CONSTRAINTS
• REFERENTIAL INTEGRITY CONSTRAINTS
12. • DOMAIN CONSTRAINTS
DOMAIN CONSTRAINTS CAN BE VIOLATED IF AN ATTRIBUTE VALUE IS NOT
APPEARING IN THE CORRESPONDING DOMAIN OR IT IS NOT OF THE APPROPRIATE
DATA TYPE.
• KEY CONSTRAINTS
AN ATTRIBUTE THAT CAN UNIQUELY IDENTIFY A TUPLE IN A RELATION IS CALLED
THE KEY OF THE TABLE. THE VALUE OF THE ATTRIBUTE FOR DIFFERENT TUPLES IN
THE RELATION HAS TO BE UNIQUE.
13. Referential integrity constraints
Referential integrity constraints is base on the concept of Foreign Keys. A foreign key is an important attribute of a relation which
should be referred to in other relationships. Referential integrity constraint state happens where relation refers to a key attribute of a
different or same relation. However, that key element must exist in the table.
Example:
14. KEYS:AN ATTRIBUTE OR ATTRIBUTES USED FOR
UNIQUE IDENTIFICATION OF RECORDS IN A TABLE
15. •PRIMARY KEY: ATTRIBUTE SELECTED FOR UNIQUE
IDENTIFICATION OF RECORDS BY THE DEVELOPER FOR A
TABLE/RELATION.PRIMARY KEY SHOULD BE UNIQUE AND
NOT NULL.
•CANDIDATE KEY: MINIMAL SUPER KEY
•SUPER KEY: SET OF ONE OR MORE ATTRIBUTES THAT CAN
UNIQUELY IDENTIFY ROWS/RECORDS IN A RELATION.
•FOREIGN KEY: AN ATTRIBUTE/FIELD IN ONE TABLE THAT
REFERS TO PRIMARY KEY OF OTHER TABLE
19. RELATIONAL ALGEBRA
RELATIONAL ALGEBRA IS A PROCEDURAL QUERY LANGUAGE, WHICH TAKES INSTANCES OF RELATIONS AS INPUT AND YIELDS
INSTANCES OF RELATIONS AS OUTPUT.
• THE FUNDAMENTAL OPERATIONS OF RELATIONAL ALGEBRA ARE AS FOLLOWS −
• SELECT
• PROJECT
• UNION
• INTERSECTION
• SET DIFFERENCE
• CARTESIAN PRODUCT
• RENAME
• JOIN
• DIVISION
30. NORMALIZATION
• DATABASE NORMALIZATION IS A DATABASE SCHEMA DESIGN TECHNIQUE, BY
WHICH AN EXISTING SCHEMA IS MODIFIED TO MINIMIZE REDUNDANCY AND
DEPENDENCY OF DATA. NORMALIZATION SPLITS A LARGE TABLE INTO
SMALLER TABLES AND DEFINE RELATIONSHIPS BETWEEN THEM TO INCREASE
THE CLARITY IN ORGANIZING DATA.
• ANOMALIES IN DBMS
THERE ARE THREE TYPES OF ANOMALIES THAT OCCUR WHEN THE DATABASE IS
NOT NORMALIZED. THESE ARE – INSERTION, UPDATE AND DELETION ANOMALY.
31. NORMALIZATION
• FIRST NORMAL FORM(1NF): EVERY CELL HAS ATOMIC VALUES
• SECOND NORMAL FORM(2NF): NON-KEY ATTRIBUTES ARE DEPENDENT ON KEY
ATTRIBUTES
• THIRD NORMAL FORM(3NF): NO TRANSITIVE DEPENDENCY(EX. A=B AND B=C IS
TRANSITIVITY)
• BOYCE & CODD NORMAL FORM (BCNF): DETERMINANT SHOULD BE A CANDIDATE
KEY.(IN A FUNCTIONAL DEPENDENCY A->B ,A IS DETERMINANT AND B IS
DEPENDENT)
• FORTH NORMAL FORM(4NF): NO NON-TRIVIAL MVD(MULTIVALUED DEPENDENCY)
• FIFTH NORMAL FORM(5NF):NO JOIN DEPENDENCY
