Set difference, Database Management System

Assignment Help:

Set Difference

If R1 and R2 are two union compatible relations or relations then result of R3 =R1- R2 is the relation that have only those tuples that are in R1 but not in R2.

Incase, R3 will have tuples such that R3 = {t | R1 ∋ t ∧ t∉R2}.

 

Example:

 

R1

 

X

Y

A1

B1

A7

B7

A2

B2

A4

B4

 

 

 

  R2  

A

B

A1

B1

A2

B2

A3

B3

A4

B4

 

 

R1-R2 =

 

 

 

R1-R2 =

A

B

A3

B3

 

R2-R1=

 

 

 

R2-R1=

A

B

A7

B7

 

 

 

Note: -1) Difference operation is not commutative, i.e.,

 R1 - R2 ≠ R2 - R1

2) Difference operation is not associative, i. e.,

R1 - (R2 - R3) ≠ (R1 - R2) - R3


Related Discussions:- Set difference

Illustrate the state model for the atm class, Illustrate the State model fo...

Illustrate the State model for the ATM class let us take state model for the ATM class given below in Figure showing state model of the ATM class and the pseudo code derived fr

Working and processing files, 1.  Define each of the following IN YOUR OWN ...

1.  Define each of the following IN YOUR OWN WORDS: (a)   File: (b)   Record: (c)   Field: (d)   Primary Key: (e)   Secondary Key: 2.  A travel agency wants t

What is object oriented model, What is Object Oriented model? This mod...

What is Object Oriented model? This model is based on collection of objects. An object has values stored in instance variables with in the object. An object also having bodies

Explain er relationship model, Explain ER Relationship model? An entity...

Explain ER Relationship model? An entity-relationship model (ERM): An entity-relationship model (ERM) is an abstract theoretical illustration of structured data. Entity-relatio

Whst is logical schema, Whst is logical schema ? Logical schema is the ...

Whst is logical schema ? Logical schema is the entire database.

Explain disadvantages of a dbms, Question : (a) Database Management Sy...

Question : (a) Database Management Systems (DBMS) is the foundation of business intelligence. Explain the following concepts related to DBMS: (i) Entity Relationship Diagr

What are the failures of controlling events between objects, What are the f...

What are the failures of Controlling Events Between Objects  Failure Unintentional termination of system. Several possible causes: failure of system hardware, o

What is a transaction? , What is a transaction ? The Transaction is a un...

What is a transaction ? The Transaction is a unit of data processing. For instance, many of the transactions at a bank may be withdrawal or deposit of money; transfer of money f

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd