What is nested queries explain in details, Database Management System

Assignment Help:

What is Nested Queries explain in details?

Nested Queries - A SELECT query could have subquery(s) in it. While a SELECT query having another SELECT query in it, is known as nested query. A few operations cannot be performed along with single SELECT command or along with join operation. There are some operations that can be performed along with the help of nested queries (also referred to as subqueries). For instance, we want to calculate the second highest salary:

SELECT MAX(SAL) FROM EMP WHERE SAL < (SELECT MAX(SAL) FROM EMP)

Some operations can be performed both through Join and subqueries. The Join operation is costlier in terms of space and time. Thus, the solution based on subqueries is preferred.


Related Discussions:- What is nested queries explain in details

Explain degree of relation, Explain degree of relation? Degree of a Re...

Explain degree of relation? Degree of a Relation - The degree or arity of a relation is the number of attributes n of its relation schema.

Management information system, management information system based on funct...

management information system based on functional organisation

Define two phase commit, Define Two phase commit Two phase commit: To m...

Define Two phase commit Two phase commit: To make sure atomicity, all the sites where a transaction is being executed must agree on the final outcome of the execution. The tran

Normalise data to third normal form, A software contract and consultancy fi...

A software contract and consultancy firm maintains details of all the various projects in which its employees are currently involved. These details comprise: Employee Numbe

What are the three classes of sql expression, What are the three classes of...

What are the three classes of SQL expression? SQL expression consists of three clauses:  Select  From  Where

Dbms built for online transaction processing, Problem: A DBMS built for...

Problem: A DBMS built for Online Transaction Processing (OLTP) is usually regarded as unsuitable for data warehousing. Each system is designed with a different set of requireme

In an e-r diagram how attributes are represented, In an E-R diagram how att...

In an E-R diagram how attributes are represented ? In an E-R diagram attributes are represented in a ellipse.

Read-set(t) and timestamps-optimistic concurrency contents, read-set(T) : E...

read-set(T) : Each data items that are read by a transaction T Timestamps : for all transaction T, the start-time and the end time are reserved for all the three phases.

Create a customer database and apply queries, For the question given below,...

For the question given below, you are required to submit design and implementation documentation as described over the page. Design, implement (in Java), test and document a set of

Differentiate between b-tree and b+ tree, Differentiate between B-tree and ...

Differentiate between B-tree and B + tree    Ans:  A B-tree (or Balanced Tree) is a search tree along with additional constraints that makes sure that the tree is all the time

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