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

Define 1 nf normal form, 1 NF Normal Form The domain of attribute must...

1 NF Normal Form The domain of attribute must add only atomic (simple, indivisible) values First normal form (Minimal Form or 1NF) is a normal form need in database normalizat

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

Accessing information permissions users, Accessing information about permis...

Accessing information about permissions to all users- Object level permissions: With the use of data dictionary you can see the permissions to user. Let us get the table name fro

Define what Immediate database modification technique uses, Define what Imm...

Define what Immediate database modification technique uses?  Ans: Both undo and redo.

Data base model, why are older data base model are being replaced by new da...

why are older data base model are being replaced by new data model

What are metrics for choosing the best algorithm, What are metrics for choo...

What are metrics for choosing the best algorithm? Matrices for choosing the best algorithms are as below: Computational complexity Ease of understand ability and im

How to rearrange classes and operations, Rearrange Classes and Operations ...

Rearrange Classes and Operations Sometimes, the similar operation is defined across different classes and can easily be inherited from a familiar ancestor, but more often oper

What are the different integrity constraints in rdbms, What are the differe...

What are the different integrity constraints in RDBMS? The various integrity constraints in RDBMS are as: Primary Key: primary key is a grouping of one or more attributes

Er model, There are a number of possible solutions to the open ended brief....

There are a number of possible solutions to the open ended brief. One of the simple ones is shown here without the PKs and FKs. It is important to think of how a number of tasks

Table handling, Table Handling  In RDBMS more than one table can be tac...

Table Handling  In RDBMS more than one table can be tackled at a time by using join operation. Join operation is a relational operation that causes 2 tables with a common domai

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