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

#cursor, #what is cursor its uses ? Explain it

#what is cursor its uses ? Explain it

Database manager, Database Manager It is the interface among low-leve...

Database Manager It is the interface among low-level data, queries and application programs. Databases typically need a large amount of storage space. It is kept on disks, as

Adding redundant associations for efficient access, Adding Redundant Associ...

Adding Redundant Associations for Efficient Access Redundant associations do not add any type of information, therefore during design we should actually examine structure of o

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

Explain the cascadeless schedule, Explain the Cascadeless Schedule A ca...

Explain the Cascadeless Schedule A cascadeless schedule is one in which for every pair of transactions Ti and Tj like that Tj reads a data item before written by Ti, the commit

Explain the dependency relationship of object oriented, Explain the depende...

Explain the dependency relationship of object oriented A dependency is a relationship which states that a change in specification of one thing can affect another thing, but n

Normalization-e-r mapping , Normalize the following table upto and includin...

Normalize the following table upto and including the 3NF. Submit a 1 page printout of only the final set of normalized tables in Data Architect. Just use Data Architect to do the t

Define query language, Define query language?   A query is a statement ...

Define query language?   A query is a statement requesting the retrieval of information. The portion of DML that includes information retrieval is known as a query language.

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