DAT A BASE MANAGEMENT SYSTEM NOTES .pptx

MODULE 1
Database System Applications
VEERESH KUMAR S
Assistant Professor
Department of IT
SMEC.

Introduction to DBMS
VEERESH KUMAR S Date : 07-03-2022
Assistant Professor
Department of IT
SMEC.

Introduction
●
Data : any fact that can be recorded – text, numbers, images,
videos
●
Database : collection of related data (Student –
rollno,name,class,collegename,address,phn no, photo,marks
etc)
➢
Traditional DB – text & num
➢
Multimedia DB – videos, pics
➢
Geographical information system – images
➢
Realtime DB – day to day data
➢
Data warehouse – kind of DB which stores hue & historical
data

Cntd...
●
Database Management System (DBMS) : software
or programs that helps to define, construct, manipulate
DB.
●
DB + DBMS --> DBS (Database System)

Historical Perspective
●
Started in early 1960’s
●
Integrated Data Store (IDS)
●
Developed by Charles Bachman
●
Represented as Network Data Model.

Cntd...
●
Late 1960’s
●
Information Management System
●
Developed by IBM
●
Data representation – Hierarchical data model

Cntd...
●
In 1970’s
●
Relational data model – developed by Edgar Codd

Cntd...
●
1980’s
●
SQL (structured query language) query language –
developed as part of IBM’s system R project
●
Standard query language
●
1980-1990’s – advances (DB2, Oracle 8, Datawarehoue
etc)
●
2020 – MySQL, MongoDB, Microsoft SQL server etc

File System versus A DBMS
●
What was before DBMS? - file systems
●
Drawbacks of previous system
●
Benefits of DBMS
●
Before DBMS – file system
●
File system – store files in an individual system
(hierarchical model) – associated OS
●
Drive (c,d,e,f) – folder – sub folder – sub folder - document

Drawbacks of file systems
●
Storing data as an Operating system files
1)Huge main memory required to store data (>500gb)
2)Need programs to identify all data items - complexity
3)Couldn’t work with client – server architecture – 1 server
with n number of clients
4)Inconsistent changes – complexity
5)Not flexible to apply security policies

Why we need to use DBMS? (Advantages)
●
Data Independence – data represent & storage individually
●
Efficient Data Access – store & retrieve data efficiently
●
Data Integrity and Security
●
Data Administration
●
Concurrent Access and Crash Recovery
●
Reduced Application Development Time

Storing data in a DBMS – Data Model
●
DBMS – store data in terms of a data model
●
Data model – describes & organize data
➢ Introduce data abstraction (hide irrelevant details)
➢ Standardize how data relate to each other (sname,sid)
➢ Eg: Network data model, hierarchical data model, relational
data model, semantic data model etc.
Relational model
●
Stores data in form of relations (tables)
●
Table – columns & rows

Cntd...
●
Schema – Description of data in terms of a data model
●
Schema for a relation(table) – name of field or attributes, types.
●
Students(sid: integer, name: string, login: string, dept: string,
age: integer, gpa: real)
●
6 fields or attributes and its types as indicated
sid name login dept age gpa
101 Rahul rah11 CSE 19 8.3
202 Jay ja102 ME 22 7
411 Shanti sh222 CSE 20 9.2

Cntd...
●
Each row is a record that describes a student
●
Every record follows the schema of the Students relation.
●
Schema – template for describing a student
●
Integrity constraints – conditions that the record must
satisfy.
●
Eg: every student must have a unique sid value
●
Age should be above 17

Levels of Abstraction
●
Hiding irrelevant details from user – Data abstraction.
●
3 levels of abstraction :
➢
Physical level (Physical schema,internal
schema)
➢
Logical level (Conceptual schema)
➢
View level (external schema)

Cntd...
Physical Level
●
Lowest level of abstraction
●
Describes how data is actually stored in a db
●
Described as blocks of storage (bytes,gb, tb etc) in
memory.
●
Need to decide what file organizations to use to store the
relations – db owner
●
Need to create auxiliary data structure called indexes.
Table Name Loc
Students details

Cntd...
Logical level (conceptual schema)
●
Middle level of abstraction
●
Describes what data is stored in db.
●
Describes stored data in terms of data model.
●
Each collection of relationships can be described as a relation.
●
Students(sid: integer, name: string, login: string, dept: string,
age: integer)
●
Marks(sid: integer, marks: integer)
●
Faculty(fid: string, fname: string, dept: string, sal: real)
●
Courses(cid: string, cname: string, credits: integer)

Cntd...
External level
●
Highest level of abstraction
●
Describes user interaction with database systems
●
Data is customized at the level of individual users.
●
External schema design is guided by end user requirements
●
View : Courseinfo(cid: string, fname: string, rid: integer)
●
In a DB – one physical schema, one conceptual schema,
several external schemas

Data Independence
●
Modify schema in one level without altering another
level
●
2 types:
➢
Logical data independence
➢
Physical data independence

Cntd...
Logical data independence
●
changing conceptual schema without changing external schema
●
Due to Logical independence, any of the below change will not
affect the external layer.
➢
Add/Modify/Delete a new attribute, entity or
relationship is possible without a rewrite of existing
application programs
➢
Merging two records into one
➢
Breaking an existing record into two or more records

Cntd...
Physical data independence
●
changing internal schema without changing conceptual schema
●
easy to achieve physical data independence.
●
Due to Physical independence, any of the below change will not affect
the conceptual layer.
➢
Using a new storage device like Hard Drive or
Magnetic Tapes
➢
Modifying the file organization technique in the
Database
➢
Switching to different data structures.
➢
Modifying indexes.
➢
Change of Location of Database

Queries
●
How many students are enrolled in CSE?
●
What is the average salary of professors who teach the course ME?
●
Questions involving the data stored in a DBMS – Queries
●
Query language – query can be posed
●
Data Manipulation Language (DML) – insert, update, delete
●
Data definition language (DDL) – create, drop, alter, truncate,
comment, rename
●
Data Query language (DQL) – select
●
Data control language (DCL) – grant and revoke
●
These are collectively referred as data sublanguage when
embedded within a host language (Java, C, C++ etc)

Cntd...
●
Users
●
Query processor
●
Storage manager
●
Disk storage

Cntd...
●
Users
●
Naive users
●
Application programmers
●
Sophisticated users
●
Database administrators

Cntd...
●
Query processor
●
Compiler & linker
●
Application program object code
●
DML queries
●
DML compiler & organizer
●
Query evaluation engine
●
DDL interpreter

Cntd...
●
Storage manager
➢
File manager
➢
Buffer manager
➢
Authorization & integrity manager
➢
Transaction manager

People who work with Databases
●
End users
➢
Who wish to use db(store & use data)
➢
Little technical knowledge
●
Database implementors
➢
Build DBMS s/w
➢
Work for vendors (IBM, Oracle etc)
➢
Sophisticated users – writing own queries to access
db.

Cntd...
●
Database application programmers
➢
Develop packages that facilitates data access for end users
➢
Use software tools that vendors provide (spreadsheet,
report writers, statistical packages etc)
●
Database Administrators (DBA)
➢
Owns db
➢
Design & maintain db
➢
Design conceptual & physical schema – interact with users
and decide what data to store (conceptual) and how to
store (physical)

Cntd...
➢
Security & Authorization – unauthorized
data access is not permitted
➢
Data availability & recovery from failure -
restore
➢
Database tuning – modifying db (conceptual
& physical) for better performance.

Database Design
Relational database
●
Collection of organized & related data on a related subject
or topic.
●
This data is organized into sets (relations or tables) and
each set of data is related to another set of data based on
some rules
Student
Name
Rollno
Dept
Marks
Mid -1
Mid-2
Final

4 main stages of database development
●
Problem specification
●
Conceptual model – Logical(what data user need to store)
– User’s view – ER model – (Entity-Relationship model)
●
Implementation model – physical(how) – Developer’s view
– Relational model
●
Relational database

Database Design
●
Requirement analysis – interact with user
●
Conceptual database design – describe data – ER model
●
Logical database design - convert conceptual design
(pictorial) to relational design (tables)
●
Schema refinement – identify prblms & refine
●
Physical database design – workloads & improve
performance (clustering of tables, indexing)
●
Application & security design

Entity Relationship model
●
Represent collected requirements in terms of diagrams (pictorial representation) –
ER diagrams
●
Entity – thing (object or noun) – eg: Person
●
Attributes – Properties of object – eg: Name, age, Dept, place
●
Relationship – association – eg: studied in
●
eg: Rahul from Mumbai works for Infosys
●
Student from IT studied Python
●
Entity
●
Entity type (Schema) & Entity (instance)
●
eg: PERSON(Name, Age, Dept) --> Entity type/ schema
Rahul, 21, CSE --> Entity

Cntd...
●
In ER diagram – represent entity types
●
ER diagram helps to communicate b/w developer & normal
user
Person
Name Age Dept
Phn No

Cntd...
Attributes
●
Describes entities
●
More attributes – more information will get about an entity
●
Types:
➢Composite vs Simple attributes
➢Single valued vs multi valued attributes
➢Stored vs derived attributes
➢Complex attributes

Cntd...
●
Simple – cannot divide further
●
Composite – collection of simple attributes
●
composite
●
simple attributes
●
Multivalued – multiple values can assign
●
Single valued – only one value can assign
Person
Name Age Dept
FN LN
MN
Phn No.
Ph No2
Ph No1
address
HNo SN City

Cntd...
●
Stored – store data in database
●
Derived – derive data from stored whenever required
●
Complex – collection of composite & multivalued attribute
●
address – Hno, sn, city, state (composite)
●
address – ofc addrs, house adrs (multivalued)
Person
Name Dept DOB
Age

Cntd...
●
Name - composite
●
Age – simple, single, derived
●
Dept – single, simple
●
Address – multivalued, composite
●
Phn No - multivalued
●
DOB – stored, single, simple
●
dd, mm, yy - composite

Practice Qs
Must have minimum 4 attributes
●
Train
●
Reservation
●
Ticket
●
Passenger
●
Cancellation
●
Note : Key attribute – unique identification key to represent
entity type. Represented by ellipse and underlined text.
reservation
PNR Name Dest
Arr Time
date

Cntd...
Relationship
●
Association among entities
●
eg: Employee works for a Department
●
Entity Relation Entity
●
student writing exams
●
HOD manages a department
Employee Department
Works for
E1 Works for D1

Cntd...
●
Types
➢
One to one relationship (1:1)
➢
One to many relationship (1:N)
➢
Many to many relationship (M:N)

One to many (1:N)
Employee Works for Dept
●
Every employee exactly works for a dept & a dept can
have many employees or zero employees
●
E1
●
E2
●
E3
●
E4
●
E5
●
E6
●
D1
●
D2
●
D3
D = 2
C = 1 C = N
P = 1 P = 0

Cntd...
●
Degree : number of participants in a relation
●
Cardinality ratio : maximum number of relationships in
which an entity can participate
●
Participation / existence (minimum cardinality) : minimum
number of relationships an entity can participate
●
Structural constraints – cardinality ratio & participation

Cntd...
●
Cardinality ratio / single line / double line
●
Min – Max representation
E1 Works for D1
Employee Works for Department
N 1
Total participation Partial participation
(1,1)
(0,N)

One to one (1:1)
HOD Manages Dept
●
Every Dept should have a HOD and only one HOD can manage
one dept.
H1
H2
H3
H4
H5
●
CSE
●
ECE
●
IT
●
CE
●
ME
D = 2
C=1
P=1
C=1
P=1

Cntd...
●
●
HOD Manages Department
HOD Manages Department
1 1
(1,1) (1,1)

Many to many (N:M)
Employee Works on Project
●
Every employee exactly work on a project or multiple projects
& every project supposed to have one or many employees
●
E1
●
E2
●
E3
●
E4
●
E5
●
E6
●
P1
●
P2
●
P3
D=2
C=N
P=1
C=M
P=1

Cntd...
●
●
Employee Works on project
Employee Works on project
M N
(1,N)
(1,M)

Descriptive Attributes
●
Used to record information about a relationship
April 2010

Degrees in Relationship
1)Unary
2)Binary
3)Ternary
4)N-ary
Unary
●
Degree – 1
●
One entity is participating in the relation
Student Manages

Binary
●
Degree – 2
●
2 entity type will participate
●
Ternary
●
Degree – 3
●
3 entity types are participating
Person Account
has
1 N
Employee department
Location
Works for

N-ary
●
Degree – n
●
N number of entities are participating
●
Not popular
Entity1 Entity3
Entity2
Entity4 Entity5
Relation1

Additional features of the ER Model
●
Key constraints
●
Participation constraints
●
Weak entities
●
Class hierarchies
●
Aggregation

Key constraints
●
Constraints - rules that are to be followed while entering
data into columns of the database table
●
Eg: HOD should manage a single department
●
Student shd have an IDno
HOD Dept
Manages
1 1

Participation constraints
●
Total and partial participation
●
All the candidates need to enter regno (name, place , dob
are not mandatory)– partial participation
●
All the questions are mandatory – total participation
Employee Works for department
Total Partial
Student Quest (10)
attends

Weak Entities
●
Key attribute (primary key) – uniquely identifies each entity
in an entity set
Employee Worksfor Department
Eid Name
Place
Did Name
Building

Cntd...
●
The entity sets which do not have sufficient attributes to form a
primary key are known as weak entity sets
●
Strong entity - entity sets which have a primary key (eg:
employee & department)
●
Weak entity – cannot be identified by their own, always
depends on strong entity
●
Weak entities make a relation with strong entities through
Identifying relationship
●
Weak entities always show total participation with identifying
relationship

Cntd...
●
Representation
Identifying relationship

Class hierarchies
●
classify the entities in an entity set into subclasses
➢
Specialization
➢
Generalization
Specialization (top down approach)
●
Classifying entities into sub entities based on some
specialities
Employee
Developer Designer
Name Sal
ProjectId
IS A
tester
Team leader

Cntd...
Generalization (bottom up approach)
●
process of identifying common characteristics from a
collection of entity sets and creating a new set that
possesses these characteristics.
Account
Savings Current
IS A
Bike Bus
Car
Vehicle
Is a

Aggregation
●
Relation between 2 entities will treated as a single entity
Employee Project
Manager
Works on
Manages

Conceptual Design with the ER Model
●
Entity versus Attribute
●
Entity versus Relationship
●
Binary versus Ternary Relationships
●
Aggregation versus Ternary Relationships

Entity versus Attribute
●
Address – entity or attribute (depend upon
requirement analysis)
●
Issue
Employee Department
Id Name
Place
from to Did Dname
Budget
Works in
E1 worksin D1 from jan to mar
E1 worksin D2 from jan to mar

Cntd...
●
Solution
Employee Works in Department
Id Name
Place
Did Dname
Budget
Duration
from to
DurId
E1 Workin D1 during Dur11
E1 Workin D2 during Dur11

Entity versus Relationship
●
Issue
Employee Department
Id Name
Place
since budget Did Dname
Budget
Manages
manager
E1
E2
E3
E4
D1
D2
D3
Jan 2020 9500
Dec 2018 6000
E4 manages(9500) D1 and D2

Cntd...
●
Solution
Employee Manages Department
Id Name Did Dname
Budget
Since
Place
Is
A
Manager
budget
E4 is a manager (4500) manages D2
E4 is a manager (5000) manages D1

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