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

Explain the form of the create view command, We define a view in SQL throug...

We define a view in SQL through using the create view command. To describe a view, we must provide the view a name and must state the query in which computers the view. The form of

Relationship for college database, Using the concepts defined previous, we ...

Using the concepts defined previous, we have identified that strong entities in COLLEGE database are FACULTY, STUDENT, COURSE and DEPARTMENT. This database also has one weak entity

We need help in booking system for golf business, We need help in Booking S...

We need help in Booking System for Golf Business Development of a web based booking system which permits clients to book golf lessons with the following features- a) 4 user p

What is completeness constraint on generalization, What is completeness con...

What is completeness constraint on generalization? Define the variation between total and partial design constraint. Give an example each.       Ans: Completeness Constraints

Obtain the house numbers street wise from database, For the relations answe...

For the relations answer the following queries in SQL Street (name, location, city) House (number, street_name) Lives (name, house_number) (i) Obtain the names of persons who liv

Components of database manager, Components of database manager The ab...

Components of database manager The above functions are reached by the database manager. The major elements of a database manager are: Authorisation control: This mod

Benefits and drawbacks of heap files, Benefits of heap files 1.   This i...

Benefits of heap files 1.   This is a easy file Organisation method. 2.   Insertion is somehow capable. 3.   Good for bulk-loading data into a table. 4.   Best if file

Calculate the record size r in bytes, An employee record has the following ...

An employee record has the following structure struct employee { int eno; char name[22]; float salary; char dept[10];}; (i) Calculate the record size R in bytes.

Explanation of system architecture of dbms, Q.   With the help of a suitabl...

Q.   With the help of a suitable diagram gives module wise explanation of system architecture of DBMS. Sol. A Database management is a collection of interrelated data and col

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