Explain projection operation distribute over union operation, Database Management System

Assignment Help:

Illustrate the statement 'Projection operation distributes over the union operation'. Give an example.

Ans: Π_L(E₁ ∪ E₂) = (Π_L(E₁)) ∪ (Π_L(E₂))

This says that result acquired by projecting on an attribute set A, after taking union of two relations is similar as union of two relations each of which is a projection of original relations on A.

Related Discussions:- Explain projection operation distribute over union operation

Explain the function of input controls, Explain the function of input contr...

Explain the function of input controls. Identify four types of input control and explain the function of each. Provide an example of a data integrity error that could occur i

Describe five main functions of a database administrator, Describe five mai...

Describe five main functions of a database administrator. Ans: A database administrator (DBA) is a person who is accountable for the environmental aspects of a database. Genera

What is difference between truncate and delete, What is difference between ...

What is difference between TRUNCATE and DELETE? - Truncate can't be rolled back whereas Delete can be. - Truncate keeps the lock on table whereas Delete keeps the lock on ea

How many types of data independence have, Types of data independence D...

Types of data independence Data independence can be classified into the following two types: Physical Data Independence: This means that for any change made in the physi

Define lock, Define lock? Lock is the most common used to execute the r...

Define lock? Lock is the most common used to execute the requirement is to permit a transaction to access a data item only if it is currently holding a lock on that item.

Back up files, what is the importance of back up files

what is the importance of back up files

Column constraints-on delete cascade, CREATE TABLE prodtrans ( pno ...

CREATE TABLE prodtrans ( pno number (4) ptype char (1) CHECK (ptype in ('I','R','S')), qty number (5) FOREIGN KEY pno REFERENCES product (pno) ON DELETE CASCADE);

Data fragmentation in distributed database system, brief history,definition...

brief history,definition,current trends and future trends if any of data fragmentation

Enforce referential integrity, Use Access 2007 to create a database calle...

Use Access 2007 to create a database called UniLib.mdb. - this file should be created on your personal drive at the university (or C: if you're using Access 2007 at home) and t

Fragmentation, let us consider a table having 2200 records and the fixed si...

let us consider a table having 2200 records and the fixed size of the table to be considered as 25.then how many numbers of table is requredto perform horizontal fragmentation

Write Your Message!

Name

Email id

Message

Verfication Code

User Account

All Pages