Union - basic set operation, Database Management System

Assignment Help:

UNION

If R1 and R2 are two union compatible relations then R3 = R1 ∪ R2 is the relation having tuples that are either in R1 or in R2 or in both.

In case, R3 will have tuples such that R3 = {t | R1 ∋ t ∨ R2 ∋ t}.

Example

R1                                                                               

 

X

Y

A1

B1

A7

B7

A2

B2

A4

B4

R2

A

B

A1

B1

A2

B2

A3

B3

A4

B4

R3 = R1 ∪ R2 is

 Q

A

B

A1

B1

A2

B2

A3

B3

A4

B4

A7

B7

 

 

Note:  1) Union is a commutative operation, i.e, R ∪ S = S ∪ R.

2) Union is an associative operation, i.e.

R ∪ (S ∪ T) = (R ∪ S) ∪ T.


Related Discussions:- Union - basic set operation

Schema, difference between internal schema and external schema in DBMS

difference between internal schema and external schema in DBMS

Write modified version of transfer that avoids deadlock, Your OS has a set ...

Your OS has a set of queues, each of which is protected by a lock. To enqueue or dequeue an item, a thread must hold the lock associated to the queue. You need to implement an a

CMIS 420 Homework Assignment 2, describe all the tables you have created. ...

describe all the tables you have created. ?get table_name, status, num_rows, user_stats in user_tables system view ?get table_name, constraint_name, constraint_type in user_constr

What do you mean by persistence, What do you mean by persistence? How you w...

What do you mean by persistence? How you will make your data persistent? Persistent data is the data, which has a longer lifetime than program which has created it. Enabling th

Client dbms, i need to submit in this topic.

i need to submit in this topic.

Discuss the method for a hash file to expand shrink dynamic, Discuss the me...

Discuss the methods for a hash file to expand and shrink dynamically. What are the advantages and disadvantages of each? The hashing methods that permit dyanamic file expansi

What is the main goal of raid technology, What is the main goal of RAID tec...

What is the main goal of RAID technology? Describe the levels 1 through 5. RAID stands for Redundant Array of Inexpensive (or sometimes "Independent")Disks. RAID is a met

What are composite objects, What are composite objects? Objects that ha...

What are composite objects? Objects that have other objects are known as complex objects or composite objects.

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