Define the query optimisation, Database Management System

Assignment Help:

Define the Query optimisation

The query parser commonly generates a standard initial tree to correspond to an SQL query, with no doing any optimization. Such type of a canonical query tree denotes a relational algebra expression that is extremely inefficient if executed directly. A query commonly has many possible execution strategies, and the process of choosing a appropriate one for processing a query is termed as query optimization. The major guidelines that are applied throughout query optimization are:

a. Combine a cascade of selections 

b. Combine a cascade of projections

c. Commute selection and projection

d. Commuting selection with join / cartesian product Commuting projection with join or cartesian product

e. Commute projection with set operations

f. Commute selection with set operations


Related Discussions:- Define the query optimisation

Should i select imaging software that allows changes, Should I select imagi...

Should I select imaging software that allows changes? An imaging system should not give features to edit or alter images. Images generally are formed as safe and secure records

What is the need for triggers, What is the need for triggers? Triggers ...

What is the need for triggers? Triggers are useful mechanisms for alerting humans or for starting particular tasks automatically when particular conditions are met.

Data base design for a museum information system, In this practical assignm...

In this practical assignment, we will run through a complete database application development cycle, starting with the schema design, from an initial data import to database applic

Explain b-tree, What is B-Tree? A B-tree eliminates the redundant stora...

What is B-Tree? A B-tree eliminates the redundant storage of search-key values .It permits search key values to appear only once.

Why object-oriented system use the relational dbms, Why, generally does an ...

Why, generally does an object-oriented system use the relational DBMS? The reasons for using relational DBMS for OO systems could be any combination of following: a. Many or

What is nested trigger, What is Nested Trigger? A trigger can also havi...

What is Nested Trigger? A trigger can also having INSERT, UPDATE and DELETE logic within itself, so when the trigger is fired because of data modification it can also cause ano

Weak entity, Entity types that do not have any key attribute, and therefore...

Entity types that do not have any key attribute, and therefore cannot be identified independently, are known as weak entity types. A weak entity can be recognized uniquely only by

Wait-die scheme -deadlock prevention, Wait-die" scheme : The idea is based ...

Wait-die" scheme : The idea is based on non-preventive method. It is based on a simple rule:                                 If Ti requests a database resource that is held by T

What is a built-in, What is a Built-in A notation of identity is built-...

What is a Built-in A notation of identity is built-into the data model or programming language and no user-supplied identifier is needed. This form of identity is used in objec

Explain the term - handling boundary condition, Explain the term - Handling...

Explain the term - Handling Boundary Condition These are some circumstances that to be handled in any system initialization and termination. Describes how system is bro

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