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

Define deadlock detection, Define Deadlock detection If a system does ...

Define Deadlock detection If a system does not employ a few protocols that make sure deadlock freedom, after that a detection and recovery scheme should be used. An algorithm

How many types of users works on database, How many types of users works on...

How many types of users works on database? Users are differentiated through the way they expect to interact along with the system (i) Application programmers-interact with

Difference between clustered and a non-clustered index, What are the differ...

What are the difference between clustered and a non-clustered index? A clustered index is a special type of index that reorders the way records in the table are physically stor

Define the division operation of relational algebra, Define the Division Op...

Define the Division Operation of Relational Algebra Let R be a relation comprising attributes (A1,...Ap,Ap+1,...An) and S comprising attributes (Ap+1,...An)  DEF: Division

Describe the concepts of structural semantic data model, Question 1 List a...

Question 1 List and explain various Normal Forms. How BCNF differs from the Third Normal Form and 4th Normal forms? Question 2 Describe the concepts of Structural Semantic Da

Create a classification model, Use again the GE Flight Quest Data and build...

Use again the GE Flight Quest Data and build on the work done for homework 1 and 2. The goal is to create a classification model which classifies flights into "on-time" (you can de

Spanned and unspanned organisation, Spanned and unspanned organisation? ...

Spanned and unspanned organisation? Spanned and unspanned organization: If records are not permited to cross block boundaries then the organisation is called unspanned record

Explain growing phase of locking, Explain Growing Phase of locking Grow...

Explain Growing Phase of locking Growing Phase: In this phase the transaction can only obtain locks, but cannot release any lock. The transaction enters the growing phase as so

Commercial database architecture, At its most essential level the DBMS arch...

At its most essential level the DBMS architecture can be divide into two parts: the back end and the front end. The back end is responsible for managing the physical database an

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