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

Key, Q.   Explain the terms key constraints participation constraints and m...

Q.   Explain the terms key constraints participation constraints and mapping caradinalities in ER model.  Participation Constraints :   The participation of an entity set E i

Explain discretionary access control, Problem: (a) Given the following ...

Problem: (a) Given the following relation: Stats(Name,Sex,Children, Occupation, Salary, Tax, Audits) Write SQL code to define the following security constraints: (i) User

List any two disadvantages of a database system, List any two disadvantages...

List any two disadvantages of a database system ? The disadvantages of database system are: • Database systems are difficult, complex, and time-consuming to design. • Substanti

Objectives-database recovery and security, Objectives Define the te...

Objectives Define the terms RECOVERY and INTEGRITY; Define Recovery Techniques; Explain Error and Error detection techniques, and Define types of Authorisation.

Insert - referential integrity, The insertion of a tuple in the aim of refe...

The insertion of a tuple in the aim of reference does not cause any destruction. Though, insertion of a tuple in the relation in which, we has the foreign key, for instance, in ASS

What is the highest normal form of the table - normalization, In problems 1...

In problems 1 - 4, you are given the columns of a table, and a set of functional dependencies.  Determine the normal form of this table.  Remember that the normal form is the HIGHE

What are audit trails, What are audit trails? An audit trail is a log o...

What are audit trails? An audit trail is a log of all alters to the database along with information like which user performed the change and when the alter was performed.

Stock market, need requirement analysis for database management of stock ma...

need requirement analysis for database management of stock market

Create a database of a motor bike racing club, You have a friend that runs ...

You have a friend that runs a motor bike club that holds racing events at various venues on weekends, on a monthly basis. Some venues are private race tracks and some are dirt trac

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