1CS 222 Database Management System

Spring 2010-11

Lecture 1

Lecture 1 1

Lecture 1

Korra Sathya BabuDepartment of Computer Science

NIT Rourkela1/5/2012

Data Model A Collection of concepts that can be used to describe

the structure of a database (datatypes, relationships, and constraints that should hold on the data)

Conceptual Data Models (High level) (E-R Model, UML) Provide concepts that are close to the way many users perceive

the data

Implementation (Representational) Data Models (network, hierarchical, Relational)

Represent data by using record structures (also called record based model)

Physical Data Models (low level)(Data Structures)

Lecture 1 21/5/2012

Network Model

Lecture 1 31/5/2012

Hierarchical Model

Lecture 1 41/5/2012

Relational Model

Name Number Father Phone Address

Sri 20606001 A 2462350 Rourkela

Degree or ArityDomain

Tuple

Attibute

Siva 20606002 B 2462351 Delhi

Ran 20606003 C 2462352 Chennai

Sam 20606004 D 2462353 Vizag

Lecture 1 5

Cardinality

1/5/2012

Entity Relationship Model Notation uses three main constructs

Data entities Relationships Attributes

Entity-Relationship (E-R) Diagram A detailed, logical representation of the

entities, associations and data elements for an organization or business

6Lecture 11/5/2012

2Entity Relationship Model

Entity

Weak Entity

Relationship

Composite Attribute

Derived Attribute

Lecture 1 7

Attribute

Multivalued

Key Attribute

1/5/2012

Other Data Models Object Oriented Model Object Relational Model

Lecture 1 81/5/2012

Architecture

Plan Executer

File & Access Methods

Optimizer

Parser

Operator Evaluator

Transaction

Query Evaluation

Engine

Web Forms Application Front Ends SQL Interface

SQL Commands

Lecture 1 9

Buffer Manager

Disk Space Manager

Lock Manager

ManagerRecoveryManager

Concurrency Control DBMS

System Catalog

Data Files

Index FilesDatabase

1/5/2012

Relational Languages Data Model has two elements

Mathematical Notations Operations on Data

Operations on the data Abstract Operations (Uses Abstract Query Languages)

Relational Algebra, Relational Calculus (TRC, DRC)

C i l O ti ( C i l Q L ) Commercial Operations (uses Commercial Query Languages) SQL (RA, RC), QUEL (TRC), QBE (DRC)

Abstract Query Languages were proposed by Codd (1972) toreport the minimum capability of any relational query languageusing the relational model

Lecture 1 101/5/2012

Relational Algebra Procedural Language (step by step procedure for computing the

desired answer) Has Five Basic Operations

Select (): Given a relation R and a predicate P, select tuples from R that satisfy P Project (): Given a relation R and a subset of its attributes X, return a relation which is the

same as R except that all columns not in X are left out

Union (U): Given relations R1 and R2, return a relation R3 which contains all tuples in R1 and R2 Set Difference (): Given relations R1 and R2, return a relation R3 containing all tuples in R1

that are not in R2that are not in R2

Cartesian Product (X): Given 2 relations R1and R2,.return a relation R3 whosetuples are the concatenation of tuples in R1 and R2

A query Language which has the capability of expressing all theabove five operations is said to be Complete Language Ex. SQL, QBE is a query language where as dbIII+ is not a query language

Additional Operations Rename (), Assignment (), Intersection (), Join () , Division ()

Lecture 1 111/5/2012

Additional Operators in RA Join

Basic Operation: Cartesian product followed by selection or/and projection Natural Join Theta Join (conditional Join) (Equi-Join is a special case) Outer Join

Left Outer Join, Right Outer Join, Full Outer Join

Anti Join : Opposite of Join Semi Join : (R i>F S ) Defines a relation that contain the tuples of R that

participate in the join of R with Sparticipate in the join of R with S

Intersection Basic Operation: R-(R-S)

Division Operation Divides a relation R with degree m+n by a divisor relation S of degree n and

produces a result relation of degree m Basic Operation: RS = 1,2,..,r-s (R) 1,2,..,r-s ((1,2,..,r-s (R) X S) R)

where r is the arity of R and s is the arity of S

Lecture 1 121/5/2012

3 Aggregate operations Grouping operations

1/5/2012 Lecture 1 13

ExampleSno Sname Rating Age

22 Dustine 7 45.0

29 Brutus 1 33.0

31 Lubber 8 55.5

32 Andy 8 25.5

58 Rusty 10 35.0

Sid bid day

22 101 10/10/08

22 102 10/10/08

22 103 10/08/08

22 104 10/07/08

31 102 10/10/08

bid bname color

101 Interlake Blue

102 Interlake Red

103 Clipper Green

104 Marine red

Instance of Boats

Lecture 1 14

64 Horatio 7 35.0

71 Zorba 10 16.0

74 Horatio 9 35.0

85 Art 3 25.5

95 Bob 3 63.5

31 103 11/06/08

31 104 11/12/08

64 101 09/05/08

64 102 09/08/08

74 103 09/08/08

Instance of Sailors Instance of Reserves

1/5/2012

RA Examples1. Find Names of Sailors who have reserved boat 1032. Find the names of sailors who have reserved a red boat3. Find the color of boats reserved by Lubber4. Find the names of sailors who have reserved at least one boat5. Find the names of sailors who have reserved a red boat or a green

boat6. Find the names of sailors who have reserved at least two boats7. Find the names of sailors with age above 20 who have not

reserved a red boat8. Find the names of sailors who have reserved all boats9. Find the names of sailors who have reserved all boats called

interlake

Lecture 1 151/5/2012 Lecture 1 161/5/2012