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

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.

Primary index, Primary index A primary index is a file that has a sorte...

Primary index A primary index is a file that has a sorted series of records having two columns: a block address for that key field in the data file; and the ordering key field.

Economics, Economics: It is now usually accepted that it costs less to make...

Economics: It is now usually accepted that it costs less to make a system of smaller computers with the equivalent power of a one large computer. It is more cost-effective to get s

Cataloguing, differences between a classified catalog and a dictionary cata...

differences between a classified catalog and a dictionary catalog

Define query optimization, Define query optimization. Query optimizatio...

Define query optimization. Query optimization refers to the process of search the lowest -cost method of evaluating a given query.

ER diagram in database, What is an ER diagram? Why is it used in Database m...

What is an ER diagram? Why is it used in Database management system (DBMS)?

Differentiate between a global and a local temporary table, Differentiate b...

Differentiate between a Global and a Local temporary table? - A local temporary table exists only for the duration of a connection or if defined inside a compound statement, fo

On laod, how to write a in a text and load it on mysql

how to write a in a text and load it on mysql

Data warehousing and business intelligence, I need help with data warehousi...

I need help with data warehousing and business intelligence course project about designing a data warehouse for a jewelry company that does not have one

Define serializable schedule, Define Serializable schedule Serializable...

Define Serializable schedule Serializable schedule: An interleaved schedule of much more than one transaction is known as a serializable schedule, if it is equal to some serial

Write Your Message!

Name

Email id

Message

Verfication Code

User Account

All Pages