Introduction to Database and Transactions

7/29/2019 Introduction to Database and Transactions

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Network

Model

Basic Modeling construct is Set

Set contains Owner Record type, aSet Name, a member Record Type

member Record Type achieves Manyto many Relation

Owner Record type may be memberof Owner in another set

Data Model is Simple N/W

Links and Intersections record Typesmay exist and sets between them

Complete N/W of Relationship isrepresented by several pair wise sets

In Each set some Record Types are

Owner and one or more recordtypes are Members

Usually set defines 1:M relationship,1:1 also permitted

In 1971, conference on

Data Systems Language

(CODASYL) defined N/WModel

Based on Mathematical

Set Theory

Permits Modeling of

Many-to-manyRelationship in data

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DATABASE LANGUAGES

Data Definition Language (DDL)

DDL is to Specify the Database

Schema, Create, destroy

database and database object,

Storage Structure, access

method statements

Commands for Data

Administrators

Provides facility of Constraintslike integrity constraints,

domain constarints

Data Manipulation Language(DML) /Query Language

DML to express databasequeries and updates

Allows the users to manipulate

data as organized byappropriate data model

Used to retrieve, Insert, &modify database information

Two types: 1. Procedural &

2. Non Procedural Procedural DML: What data r

needed and how to get thatdata.




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DML

DML to express database queries and updates

Allows the users to manipulate data as organized by appropriate datamodel

Used to retrieve, Insert, & modify database information

Two types: 1. Procedural &2. Non Procedural

Procedural DML: What data r needed and how to get that data

Used to transfer cause data between a run unit & database

It relies on the host language for framework to provide proceduralactivities required to manipulate.

Basic DML Commands are: SELECTSELECT *INSERTUPDATEDELETEMERGE




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DCL Domain Constraints:

* Domain-Set of Possible Values for each attribute associated with an entity set.* Specify important constraints that each instance of relation must satisfy

Referential Integrity:

Property of data which, when satisfied, requires every value of one attribute(column) of

relation (table) to exists as a value of another attribute in a different (or the same)

relation (Table)

Assertions: Condition that database must always satisfy

e.g. Domain Constraint and Referential Integrity

Authorization: Read Authorization

Insert Authorization

Update Authorization

Delete Authorization DDL Commands: CREATE DATABASE & TABLE

USE

ALTER

ADD

DROP DATABASE & TABLE




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DATABASE DESIGN Process of producing a detailed data model of Database

contains all logical and physical design choices and Physicalstorage parameter

Fully attributed data model contains detailed attributes for

each entity.

Design carried out by1. find the relationship between different Data elements,

2. Superimpose a logical structure upon data on the basis of

these relationship

To design information s/m that is based in database, the

conceptual data model is mapped to logical data model

(relational model); this in turn mapped to a physical model

during physical design. Both of these stages are referred as

Physical Design.




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Entity-Relationship Model This model is used during Requirement Analysis stage of

Information System Design. Entity - a thing which is recognized as being capable of an

independent existence & uniquely identified.

E.g. Car, house etc. It can be set as noun

Relationship -How two or more entities r related to one another. It

can be set as Verb, linking two or more nouns.

E.g. an owns relationship between Company and a computer,

a performs relationship between an artist and a song.

Attributes Entity and Relationship can both have attributes.

E.g. An employee entity might have an Employee Id. attributeProvedrelationship may have a Date attribute

Every Entity must have a minimal set of uniquely identified

attributes, called Entitys Primary Key

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Entity-Relationship Model

Diagrammatic conventions are used called EntityRelationship Diagrams (ERDs)

Entity Set -> Rectangles

Relationship Set -> Diamonds

Attributes -> Ovals connected with Lines

If Entity set participates in a relationship set, theyare connected with a line.

ERDs dont show single entities or single instanceof relations.

Continue

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Entity-Relationship

Model

A Double line : A participationconstraints i.e. totality orsurjectivity:

An arrow from entity set to

relationship set : A keyconstraint, i.e. injectivity

A thick line indicates both, i.e.

bijective An underlined name of an

attribute indicates that is a key

Entity Set ->Rectangles

Relationship Set-> Diamonds

Attributes ->

Ovalsconnected with

Lines


cardinality constraints

expressed by ERDs


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Normalization Normalization: Normalization is the process of efficiently organizing

data in a database.

There are two goals of Normalization process:1. Eliminating Redundant Data2. Ensuring data dependencies make sense

There are five normal forms through which we can normalize the

database. These forms are as following:1. First Normal Form or 1NF2. Second Normal Form or 2NF3. Third Normal Form or 3NF4. Fourth Normal Form or 4NF5. Fifth Normal Form or 5NF

Out of these five normal forms only first three are used in practical.4NF used occasionally and 5NF is used veryrarely.


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First Normal Form (1NF) :

First normal forms (1NF) sets the very basic rules

for an organized database:1. Eliminate duplicate columns from the Same Table

2. Create Separate table for each group of related dataand identify each row with the unique column orset of columns (the primary key)

Second Normal Form (2NF):Second Normal Form (2NF) further addresses theconcept of removing the duplicate data. This can beachieved by following techniques,

1. Meet all requirement s of 1NF

2. Remove subsets of Data that apply to multiple rowsof a table and place them in separate tables

3. Create relationship between these new tables and theirpredecessors through the use of Foreign Key


Normalization


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Third Normal Form (3NF) :

3NF goes one step further;1. Meet all requirement s of 2NF2. Remove columns that are not dependent

upon the primary key

Fourth Normal Form (4NF) :Meet all requirement s of 3NF

A Relation is in 4NF if it has no multi-valueddependencies.

Normalization guidelines are cumulative. For thedatabase to be in 2NF, it must full fill criteria of 1NF


Normalization



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Data Storage and Querying

DS Partitioned in to modules with each of the

separate Responsibilities.

Functional Components of DS are partitioned

into Storage Manager (SM) and Query

Processor Components (QP) SM is imp as database requires a large amt of

space for Storing data.

QP is imp as it helps DS to simplify and allowsthe system to access data


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Storage Manager (SM): Provide the interface between:1. file Manager2. Buffer Manager3. Data Integrity Manager4. Transaction Manager.

File Manager: To Manage Disk Space for the Storageand Data Structure used for Storing information.

Buffer Manager: Fetching data from Disk Storage intomain memory and decides what data are to be cachedin to memory

Data Integrity Manager: Check the IntegrityConstraints, & authority of users to access the data.

Transaction Manager: ensures that database remains ina consistent and in the correct state.


Data Storage and QueryingStorage Manager (SM)

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SM implements several data structures as apart of the Physical system implementation:

Some of them are File System, Data Dictionary,

Indices

File System: Stores data itself

Data Dictionary: Stores metadata of Database

i.e. Structure of Database in particular Schema Indices: Used to provide fast access to

database.


Data Storage and QueryingStorage Manager


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Query Processor Components are:

1. DDL Interpreter2. DML Compiler

3. Query Evaluation Engine

DDL Interpreter:

1. Interprates DDL Statements and records defn in the data dictionary. DML Compiler:

1. Translates DML Statemt in a query Language into a evaluation planand performs query Optimization.

2. Evaluation plan consists of Low-Level instructions that the QueryEvaluation Engine understand.

3. DML Compiler Also performs Query Optimization by picking thelowest cost evaluation plan among the alternatives

Query Evaluation Engine: Executes the low level instructionsgenerated by DML Compiler.


Data Storage and QueryingQuery Processor:


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Transaction Management (TM) in DBMS A Database Transaction Management ideally guarantees

ACID property

Ensures Data integrity i.e. avoid Concurrent user accessto data or Faults tolerance.

Through TM, DBMS maintain integrity by not allowingmore than one user to update same record at the Same

time. (Integrity Constraints) Through TM, DBMS can help to prevent duplicate record

via Unique Index Constraint (Unique key Constraints)

Transaction Processing allows multiple individual

operatns to be linked together a single, individual trann.

It ensures that either all operatn in a transaction arecompleted without error or none of then are.


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If some opertn are completed but error occur when others

are attempted, the transaction processing system RollBack all of the operation of the transaction (includingsuccessful one also)

If all operations of Transactions are completedsuccessfully, the transaction is committed by the systemand all changes to the database are made permanent, andthis transaction cant rollback.

Transaction Processing guards against H/W and S/W errorsthat might leave a transaction partially completed

Transactions are processed in a strict Chronological Order.i.e. if n+1th transaction deals with the same portion ofdatabase as nth transaction dealing, transaction n+1 willnot begin until transaction n is committed.


Transaction Management (TM) in DBMS

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Before any transaction is committed, all other

transaction affecting the same part of theDatabase must also be committed.

Transaction Management component ensure

that the database remains in a consistent state

despite system failure and transaction failures.

Questions: Why Transaction Management isimportant in DBMS and how we are achieving it

in DBMS?


Transaction Management (TM) in DBMS


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Data Mining and Analysis

Data Mining is a process of extracting patternsfor Data

The related terms are data dredging, data

fishing, & data snooping. Four tasks of data Mining:

1.Clustering

2. Classification3. Regression4. Association Rule Learning


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Data Mining and Analysis

Clustering: Task of discovering Groups and structuresin data that r in some way or another Similar,without know structure of database.

Classification: Task of generalizing known structure toapply to new data.

Regression: Attempt to find a function which modelsthe data with the least error.

Association Rule Learning: Searches for relationshipbetween variables.

Question: What is mean by Data Mining and what arethe tasks of Data Mining?


Database Architecture:


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Database Architecture:


Simple UserApplication

Programmer

Sophisticated

User(Analyser)

Database

Administrator

Application

Interface

Application

ProgramQuery Tools

Administration

tools

Application Program

Object Code

Query Evaluation engine

DML Compiler and

Organizer

DDL InterpreterDML QueryCompiler and Linker

Buffer Manager File ManagerAuthorization & Integrity

ManagerTransaction Manager

Data IndicesData Dictionary

Statistical Data

User Write User User

Query Processor

Storage Manager

Disk Package


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Database Architecture The architecture of Database system in depends

on the underlying Computer System on which the

database is running. Accordingly the architecture is divided into:

1. Centralized2. Client-Server

3. Parallel4. Distributed

Two-tier Architecture:* Application is partitioned into components that

resides on client machine* Client Machine directly invoke database systemat server level through Query Language Statemt.


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Three-Tier Architecture:

* Client Machine acts as merely a front-end anddoes not contain any direct call.

* Usually the client end communicates with the

application server through forms interface


Database Architecture

User User

ApplicationApplication

Client

Application

Server

Database System

Database System

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Database Users and Administrators

Database User:

* Four Types:1. Nave Users (simple User)

2. Application Programmer

3. Sophisticated Users4. Specialized Users


Documents

Introduction to Database and Transactions