good ppt for rdbms starter

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Introduction to

Database Management Systems

(DBMS)

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Database Management Database Management System (DBMS)System (DBMS)

Definitions:Definitions:

Data: Data: Known facts that can be Known facts that can be recorded and that have implicit meaningrecorded and that have implicit meaning

Database:Database: Collection of related data Collection of related data Ex. the names, telephone numbers and Ex. the names, telephone numbers and

addresses of all the people you knowaddresses of all the people you know

Database Management System:Database Management System: A A computerized record-keeping systemcomputerized record-keeping system

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DBMS (Contd.)DBMS (Contd.) Goals of a Database Management System:Goals of a Database Management System:

To provide an efficient as well as convenient To provide an efficient as well as convenient

environment for accessing data in a databaseenvironment for accessing data in a database Enforce information security: database Enforce information security: database

security, concurrence control, crash recoverysecurity, concurrence control, crash recovery

It is a general purpose facility for:It is a general purpose facility for: Defining Defining database database ConstructingConstructing database database Manipulating Manipulating databasedatabase

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Benefits of database Benefits of database approach approach

Redundancy can be reducedRedundancy can be reduced Inconsistency can be avoided Inconsistency can be avoided Data can be sharedData can be shared Standards can be enforcedStandards can be enforced Security restrictions can be appliedSecurity restrictions can be applied Integrity can be maintainedIntegrity can be maintained Data independence can be providedData independence can be provided

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DBMS FunctionsDBMS Functions

Data DefinitionData Definition Data ManipulationData Manipulation Data Security and IntegrityData Security and Integrity Data Recovery and ConcurrencyData Recovery and Concurrency Data DictionaryData Dictionary Performance Performance

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Database SystemDatabase System

Stored Data Defn. Stored Database

Software to access stored data

Software to process queries/programs

DBMS

Software

Application Programs/Queries

Users

DATABASE

SYSTEM

(META-DATA).

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Categories of Data Categories of Data ModelsModels

ConceptuaConceptuall

PhysicalPhysical RepresentationRepresentationalal

Data ModelData Model A set of concepts used to desscribe the A set of concepts used to desscribe the

structure of a databasestructure of a database By structure, we mean the data types, By structure, we mean the data types,

relationships, and constraints that relationships, and constraints that should holds for the datashould holds for the data

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Database ArchitectureDatabase Architecture

Internal level(storage view)

Conceptual level(community user view)

External level(individual user views)

Database

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An example of the three An example of the three levelslevels

SNo FName LName Age Salary

SNo FName LName Age Salary

SNo LName BranchNo

struct STAFF { int staffNo; int branchNo; char fName[15]; char lName[15]; struct date dateOfBirth; float salary; struct STAFF *next; /* pointer to next Staff record */};index staffNo; index branchNo; /* define indexes for staff */

BranchNo

Conceptual View

External View1

External View2

Internal View

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SchemaSchema Schema: Description of data in terms of Schema: Description of data in terms of

a data modela data model Three-level DB Architecture defines Three-level DB Architecture defines

following schemas:following schemas: External Schema (or sub-schema)External Schema (or sub-schema)

Written using Written using external DDLexternal DDL Conceptual Schema (or schema)Conceptual Schema (or schema)

Written using Written using conceptual DDLconceptual DDL Internal SchemaInternal Schema

Written using Written using internal DDLinternal DDL or or storage structure storage structure definitiondefinition

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Data IndependenceData Independence Change the schema at one level of a database Change the schema at one level of a database

system without a need to change the schema system without a need to change the schema at the next higher levelat the next higher level Logical data independence: Refers to the immunity Logical data independence: Refers to the immunity

of the external schemas to changes in the of the external schemas to changes in the conceptual schema e.g., add new record or fieldconceptual schema e.g., add new record or field

Physical data independence: Refers to the Physical data independence: Refers to the immunity of the conceptual schema to changes in immunity of the conceptual schema to changes in the internal schema e.g., adding new index should the internal schema e.g., adding new index should not void existing onesnot void existing ones

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HIERARCHICAL

NETWORK

RELATIONAL

TABLEROW

COLUMN

VALUE

TYPES OF DATABASE TYPES OF DATABASE MODELSMODELS

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DATA ANALYSIS

Entities - Attributes - Relationships - Integrity Rules

LOGICAL DESIGN

Tables - Columns - Primary Keys - Foreign Keys

PHYSICAL DESIGN

DDL for Tablespaces, Tables, Indexes

DATABASE DESIGN DATABASE DESIGN PHASESPHASES

Introduction to Introduction to Relational Relational Databases:Databases:

RDBMSRDBMS

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Some Important TermsSome Important Terms Relation : Relation : a tablea table

Tuple : Tuple : a row in a tablea row in a table

Attribute : Attribute : a Column in a tablea Column in a table

Degree : Degree : number of attributesnumber of attributes

Cardinality : Cardinality : number of tuplesnumber of tuples

Primary Key : Primary Key : a unique identifier for the tablea unique identifier for the table

Domain :Domain : a pool of values from which specific a pool of values from which specific

attributes of specific relations draw their valuesattributes of specific relations draw their values

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KeysKeys KeyKey

Super KeySuper Key

Candidate KeysCandidate Keys Primary KeyPrimary Key

Alternate KeyAlternate Key

Secondary KeysSecondary Keys

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Keys and Referential Keys and Referential IntegrityIntegrity

sid cid grade

53666 carnatic101 C

53688 reggae203 B

53650 topology112 A

53666 history105 B

sid name age

53666 Jones 18

53688 Smith 18

53650 Smith 19

gpa

3.4

3.2

3.8

login

Jones@cs

Smith@eecs

Smith@math

Enrolled Student

Primary keyForeign key referring tosid of STUDENT relation

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Conceptual Design Conceptual Design Using theUsing the

Entity- Entity- Relationship Relationship

ModelModel

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Overview of Database Overview of Database DesignDesign

Conceptual design : (ER Model is Conceptual design : (ER Model is used at this stage.)used at this stage.)

Schema Refinement : Schema Refinement : (Normalization)(Normalization)

Physical Database Design and Physical Database Design and Tuning Tuning

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Design Phases…Design Phases…Requirements Collection

& Analysis

Data Requirements

Functional Requirements Conceptual Design

Logical Design

Physical Design

User Defined Operations Data Flow DiagramsSequence Diagrams, Scenarios

Entity Types, Constraints , RelationshipsNo Implementation Details.

Ensures Requirements Meets the Design

Data Model Mapping – Type of Database is identified

Internal Storage Structures / Access Path / File Organizations

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E-R ModelingE-R Modeling

EntityEntity is anything that exists and is is anything that exists and is

distinguishabledistinguishable Entity SetEntity Set

a group of similar entitiesa group of similar entities AttributeAttribute

properties that describe an entityproperties that describe an entity RelationshipRelationship

an association between entitiesan association between entities

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NotationsNotations

ENTITY TYPE ( REGULAR )

WEAK ENTITY TYPE

RELATIONSHIP TYPE

WEAK RELATIONSHIP TYPE

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CREATE TABLE Employees(ssn CHAR (11),name CHAR (20),lot INTEGER,PRIMARY KEY (ssn))

Employee

ssn name lotSSN NAME LOT

123- 22- 3666Attishoo 48

231- 31- 5368Smiley 22

131- 24- 3650Smethurst 35

Entity

Entity Set

Attributes

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Types of Relationships

student ID cardIs issued

students courseenrols in

students teststake

1 1

1M

M M

1:1

1:M

M:M

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ER Model

Department

did dname budgetsincesince

Works_inEmployee

ssn name lot

Reports_To

supervisor Sub-ordinate

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CREATE TABLE Works_ In(ssn CHAR (11),did INTEGER,since DATE,PRIMARY KEY (ssn, did),FOREIGN KEY (ssn)REFERENCES Employees,FOREIGN KEY (did)REFERENCES Departments)

SSN DID SINCE

123-22-3666 51 1/1/91

123-22-3666 56 3/3/93

231-31-5368 51 2/2/92

ER Model (Contd.)

Works_ In

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ManagesDepartment

did dname budgetsince

Employee

ssn name lot

Key Constraints

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Key Constraints for Ternary Relationships

Department

did dnamesince

Works_inEmployee

ssn name lotbudget

Location

capacityaddress

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Participation Constraints

Department


ManagesEmployee

ssn name lot

Works_in

since

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policyDependent

pnameagecost

Employee

ssn name lot

Weak Entities

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ISA (‘is a’) Hierarchies

Employee

ssn name lot

Hourly_Emp

Hrs_worked

Hrly_wages

Contract_Emp

contractidIsA

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Employee

ssn name lot

monitors

project

pid pbudget Started on

department

did dname budget

sponsors

until

Aggregation

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Works_ In does not allow an employee to work in a department for two or more periods (why?)

Entity vs. Attribute

Works_inDepartment

did dname budgetfrom

Employee

ssn name lot to

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Entity vs. Attribute (Contd.)

Works_inDepartment

did dname budget

from

Employee

ssn name lot

toDuration

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managesDepartment


Employee

ssn name lot DB

DB - Dbudget

Entity vs. Relationship

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managesDepartment

did dname budget

since

Employee

ssn name lot

DBudgetMgr_apptAppt num

Entity vs. Relationship

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Dependent

pname age

cost

Employee

ssn name lot

covers

Policy

policyid

Binary vs. Ternary Relationships

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Dependent

pnameage

cost

Employee

ssn name lot

Beneficiary

Policypolicyid

Better Design

purchaser

Binary vs. Ternary Relationships

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• Some constraints cannot be captured in ER diagrams:

• Functional dependencies

• Inclusion dependencies

• General constraints

Constraints Beyond the ER Model

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E-R DiagramE-R Diagram

DEPARTMENT

DEPT_EMP

EMPLOYEE

EMP_DEP

DEPENDENT

PROJ_WORK

PROJ_MGR

PROJECT

SUPPLIER

SUPP_PART_PROJ

PART

PART_STRUCTURE

SUPP_PART

MM

M

M

M

M

M

M

M M

M

M

1

1 1

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Example to Start with ….Example to Start with ….

An Example Database Application An Example Database Application called COMPANY which serves to called COMPANY which serves to illustrate the ER Model concepts and illustrate the ER Model concepts and their schema design.their schema design.

The following are collection from the The following are collection from the Client.Client.

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Analysis…Analysis…

Company :Company :Organized into Departments, Each Organized into Departments, Each Department has a name, no and Department has a name, no and manager who manages the manager who manages the department. The Company keeps department. The Company keeps track of the date that employee track of the date that employee managing the department. A managing the department. A Department may have a Several Department may have a Several locations.locations.

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Analysis…Analysis…

Department :Department :A Department controls a number of Projects A Department controls a number of Projects each of which has a unique name , no and a each of which has a unique name , no and a single Location.single Location.

Employee :Employee :Name, Age, Gender, BirthDate, SSN, Name, Age, Gender, BirthDate, SSN, Address, Salary. An Employee is assigned to Address, Salary. An Employee is assigned to one department, may work on several one department, may work on several projects which are not controlled by the projects which are not controlled by the department. Track of the number of hours department. Track of the number of hours per week is also controlled.per week is also controlled.

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Analysis….Analysis….

Keep track of the dependents of Keep track of the dependents of each employee for insurance policies each employee for insurance policies : We keep each dependant first : We keep each dependant first name, gender, Date of birth and name, gender, Date of birth and relationship to the employee.relationship to the employee.

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DEPARTMENT ( Name , Number , { Locations } , Manager, Start Date )

PROJECT( Name, Number, Location , Controlling Department )

EMPLOYEE(Name (Fname, Lname) , SSN , Gender, Address, Salary

Birthdate, Department , Supervisor , (Workson ( Project , Hrs))

DEPENDENT ( Employee, Name, Gender, Birthdate , Relationship )

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Example …Example …

Manage:Manage: Department and Employee Department and Employee Partial Partial ParticipationParticipation

Relation Attribute : StartDate.Relation Attribute : StartDate. Works For:Works For:

Department and EmployeeDepartment and Employee Total ParticipationTotal Participation

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Example…Example…

Control :Control : Department , ProjectDepartment , Project Partial Participation from Department Partial Participation from Department Total Participation from ProjectTotal Participation from Project Control Department is a RKA.Control Department is a RKA.

Supervisor :Supervisor : Employee, EmployeeEmployee, Employee Partial and RecursivePartial and Recursive

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Example …Example …

Works – On :Works – On : Project , EmployeeProject , Employee Total ParticipationTotal Participation Hours Worked is a RKA.Hours Worked is a RKA.

Dependants of:Dependants of: Employee , DependantEmployee , Dependant Dependant is a WeakerDependant is a Weaker Dependant is Total , Employee is Dependant is Total , Employee is

Partial.Partial.

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One Possible mapping of the One Possible mapping of the Problem Statement Problem Statement

Works For Department

Name No Loc

Controls

Project

Name No Loc

WorksOn

manages

Sdate

Hours

Depend On

Name Sex Bdate

Relationship

Supervise

s

Employee Address

Fname

SexSSN

Name

Bdate

Sal

Lname

Dependent

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Schema Schema Refinement andRefinement andNormalizationNormalization

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Normalization and Normalization and Normal FormsNormal Forms

Normalization:Normalization: DecomposingDecomposing a larger, complex table into several a larger, complex table into several

smaller, simpler ones.smaller, simpler ones. Move from a lower Move from a lower normal formnormal form to a higher to a higher

Normal form.Normal form. Normal Forms:Normal Forms:

First Normal Form (1NF)First Normal Form (1NF) Second Normal Form (2NF)Second Normal Form (2NF) Third Normal Form (3NF)Third Normal Form (3NF) *Higher Normal Forms (BCNF, 4NF, 5NF ....)*Higher Normal Forms (BCNF, 4NF, 5NF ....)

In practice, 3NF is often good enough.In practice, 3NF is often good enough.

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Why Normal FormsWhy Normal Forms

The first question to ask is whether The first question to ask is whether

any refinement is needed!any refinement is needed!

If a relation is in a certain normal If a relation is in a certain normal

form (BCNF, 3NF etc.), it is known form (BCNF, 3NF etc.), it is known

that certain kinds of problems are that certain kinds of problems are

avoided/ minimized. This can be used avoided/ minimized. This can be used

to help us decide whether to help us decide whether

decomposing the relation will help.decomposing the relation will help.

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The Evils of RedundancyThe Evils of Redundancy

Redundancy is at the root of several Redundancy is at the root of several problems associated with relational problems associated with relational schemasschemas

More seriously, data redundancy causes More seriously, data redundancy causes several anomalies: insert, update, deleteseveral anomalies: insert, update, delete

Wastage of storage.Wastage of storage. Main refinement technique: Main refinement technique:

decomposition (replacing ABCD with, decomposition (replacing ABCD with, say, AB and BCD, or ACD and ABD).say, AB and BCD, or ACD and ABD).

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Refining an ER Diagram - Refining an ER Diagram - BeforeBefore

Department


Works_inEmployee

ssn name lot

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Refining an ER Diagram - Refining an ER Diagram - AfterAfter

Works_in

since

Employee

ssn name

lot

Department

did dname budget

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First Normal FormFirst Normal Form A table is in 1NF, if every row contains exactly one A table is in 1NF, if every row contains exactly one

value for each attribute.value for each attribute. Disallow multivalued attributes, composite attributes Disallow multivalued attributes, composite attributes

and their combinations.and their combinations. 1NF states that :1NF states that :

domains of attributes must include only atomic (simple, domains of attributes must include only atomic (simple, indivisible) values and that value of any attribute in a tuple indivisible) values and that value of any attribute in a tuple must be a single value from the domain of that attribute.must be a single value from the domain of that attribute.

By definition, any relational table must be in 1NF.By definition, any relational table must be in 1NF.

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Functional Dependencies Functional Dependencies (FDs)(FDs)

Provide a formal mechanism to Provide a formal mechanism to

express constraints between express constraints between

attributes attributes

Given a relation R, attribute Y of R is Given a relation R, attribute Y of R is

functionally dependent on the functionally dependent on the

attribute X of R if & only if each X-attribute X of R if & only if each X-

value in R has associated with it value in R has associated with it

precisely one Y-value in R.precisely one Y-value in R.

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Full DependencyFull Dependency

Concept of full functional Concept of full functional

dependencydependency A FD x A FD x y y is a full functional is a full functional

dependency if removal of any attribute dependency if removal of any attribute

A from X means that the dependency A from X means that the dependency

does not hold any more.does not hold any more.

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Partial DependencyPartial Dependency

An F.D. x An F.D. x y is a partial dependency y is a partial dependency

if there is some attribute A if there is some attribute A X that X that can be removed from X and the can be removed from X and the dependency will still hold.dependency will still hold.

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Example: Constraints on Example: Constraints on Entity SetEntity Set

123- 22- 3666 Attishoo231- 31- 5368131- 24- 3650434- 26- 3751612- 67- 4134

SmileySmethurstGulduMadayan

4822353535

88558

1010

77

10

4030303240

S N L R W H

58

710

R W123- 22- 3666 Attishoo231- 31- 5368131- 24- 3650434- 26- 3751612- 67- 4134

SmileySmethurstGulduMadayan

4822353535

S N L4030303240

H8R

85

58

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Second Normal Form Second Normal Form (2NF)(2NF)

A relation schema R is in 2NF if:A relation schema R is in 2NF if: it is in 1NF andit is in 1NF and

every non-prime attribute A in R is fully every non-prime attribute A in R is fully

functionally dependent on the primary functionally dependent on the primary

key of R.key of R.

2NF prohibits 2NF prohibits partial dependenciespartial dependencies..

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2NF: An Example2NF: An Example Emp{Eno, Dept, ProjCode, Hours}Emp{Eno, Dept, ProjCode, Hours}

Primary key: {Eno, ProjCode}Primary key: {Eno, ProjCode} {Eno} -> {Dept}, {Eno, ProjCode} -> {Hours}{Eno} -> {Dept}, {Eno, ProjCode} -> {Hours}

Test of 2NFTest of 2NF {Eno} -> {Dept}: {Eno} -> {Dept}: partial dependency.partial dependency. Emp is in 1NF, but not in 2NF.Emp is in 1NF, but not in 2NF.

Decomposition:Decomposition: Emp {Emp {EnoEno, Dept}, Dept} Proj {Proj {Eno, ProjCodeEno, ProjCode, Hours}, Hours}

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Transitive DependencyTransitive Dependency

An FD X An FD X Y in a relation schema R Y in a relation schema R

is a transitive dependency if is a transitive dependency if there is a set of attributes Z that is not there is a set of attributes Z that is not

a subset of any key of R, and a subset of any key of R, and both X both X Z and Z Z and Z Y hold. Y hold.

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Third Normal FormThird Normal Form A relation schema R is in 3NF if A relation schema R is in 3NF if

It is in 2NF and It is in 2NF and

No nonprime attribute of R is transitively No nonprime attribute of R is transitively

dependent on the primary key.dependent on the primary key.

3NF means that each non-key attribute value in any tuple 3NF means that each non-key attribute value in any tuple is truly dependent on the Primary Key and not even is truly dependent on the Primary Key and not even partially on other attributes.partially on other attributes.

3NF prohibits 3NF prohibits transitive dependenciestransitive dependencies..

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3NF: An Example3NF: An Example Emp{Eno, Dept, Dept_Head}Emp{Eno, Dept, Dept_Head}

Primary key: {Eno}Primary key: {Eno} {Eno} -> {Dept}, {Dept} -> {Dept_Head}{Eno} -> {Dept}, {Dept} -> {Dept_Head}

Test of 3NFTest of 3NF {Eno} -> {Dept} -> {Dept_Head}: Transitive {Eno} -> {Dept} -> {Dept_Head}: Transitive

dependency.dependency. Emp is in 2NF, but not in 3NF.Emp is in 2NF, but not in 3NF.

Decomposition:Decomposition: Emp {Emp {Eno, DeptEno, Dept}} Dept {Dept, Dept_Head}Dept {Dept, Dept_Head}

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Boyce –Codd Normal Boyce –Codd Normal FormForm

The intention of BCNF is that- 3NF The intention of BCNF is that- 3NF does not satisfactorily handle the does not satisfactorily handle the case of a relation processing two or case of a relation processing two or more composite or overlapping more composite or overlapping candidate keys candidate keys

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BCNF ( Boyce Codd BCNF ( Boyce Codd Normal Form)Normal Form)

A Relation is said to be in Boyce A Relation is said to be in Boyce Codd Normal Form (BCNF) if and Codd Normal Form (BCNF) if and only if every determinant is a only if every determinant is a candidate key.candidate key.

good ppt for rdbms starter

Education

data types

schema schema

description of data

database security

integrity data recovery

collection of related

subschema conceptual

concurrency data dictionary