Explain mechanism of nested queries, Database Management System

Assignment Help:

Explain mechanism of nested queries?

SQL gives a mechanism for nesting subqueries. A subquery is a select from where expression that is nested within one more query. A common use of sub queries is to perform tests for set membership, make set comparisons, and verify set cardinality.

a) Set membership

(select customer-name

from depositor)

b) Set comparison

select distinct T.branch-name

from branch as T,branch as S

where T.assets > S.assets and S.branch-city='Brooklyn'

a) Test for Empty Relations

Select customer-name

from borrower

where exits (select *

from depositor

where depositor.customername=borrower.customer-name)

a) Test for the Absence of Duplicate Tuples

 

 


Related Discussions:- Explain mechanism of nested queries

Candidate keys, Super keys of a relation can have extra attributes. Candida...

Super keys of a relation can have extra attributes. Candidate keys are minimal super key, i.e. such a key have no extraneous attribute. An attribute is known as extraneous if even

Example for while until, Assume you are given a uniprocessor system with on...

Assume you are given a uniprocessor system with one gigabyte of memory and a 300 gigabyte disk. The OS on the machine has a demand paged virtual memory system with a local page rep

What is de-normalization, What is De-normalization? De-normalization is...

What is De-normalization? De-normalization is the method of attempting to optimize the performance of a database by adding redundant data. It is sometimes essential because cur

Can you delete data element, Can we delete data element, which is being use...

Can we delete data element, which is being used by table fields. No we cant delete data element.

Differentiate between logical database design and physical, Differentiate b...

Differentiate between logical database design and physical database design. Show how this separation leads to data independence? Basis Logical Databas

What is a database, What is a database? Database - Basically in simpl...

What is a database? Database - Basically in simple terms A database is a collection of inter related data and/or information stored so which it is available to several users

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

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

Explain trivial dependency, Explain trivial dependency? Functional depe...

Explain trivial dependency? Functional dependency of the form α ->β. is trivial if α C β. Trivial functional dependencies are satisfied by all the relations.

Er diagram, Design a generalization–specialization hierarchy for a motor-ve...

Design a generalization–specialization hierarchy for a motor-vehicle sales company. The company sells motorcycles, passenger cars, vans, and buses. Justify your placement of attrib

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