Difference between functions along with or without grouping, Database Management System

Assignment Help:

Explain the difference between using functions along with and without grouping attributes in relational algebra. Give examples.

Ans: Group functions are used to group data of similar type.
GAMMA = grouping and aggregation
Applying GAMMAL(R)
• Group R according to all the grouping attributes on list L.
1. That is: form one group for each distinct list of values for those attributes in R.
• Within each group, compute AGG(A ) for each aggregation on list L.
• Result has one tuple for each group:
1. The grouping attributes and
2. Their group's aggregations.
Example: Grouping /Aggregation
R = ( A B C )
1 2 3
4 5 6
1 2 5
GAMMAA,B,AVG(C) (R) = ?
First, group R by A and B :
A B C
1 2 3
1 2 5
4 5 6
Then, average C within groups:
A B AVG(C)
1 2 4
4 5 6


Related Discussions:- Difference between functions along with or without grouping

Determine the minimal set of functional dependencies, Determine the minimal...

Determine the minimal set of functional dependencies for the following data. This table is part of the OHSU database of extracurricular activities and tracks the DMICE band's co

Assignment - 1 - redoing to improve grades, Assignment #1 Data Management ...

Assignment #1 Data Management The questions on this exam are based on the Baxter Aviation case scenario. 1. (5 points) The systems analyst proposes the following two relationshi

Convert encrypted hsql database into csv format, Project Description: We...

Project Description: We have an encrypted HSQL Database which we want to change into csv format. HSQL DB . We have java application (jar file) which reads that database but n

Consistency, what do you mean by consistency in rdbms?

what do you mean by consistency in rdbms?

Define the term multimedia database, Question : (a) Explain with the h...

Question : (a) Explain with the help of appropriate examples the difference between ‘Data' and ‘Information'. (b) A digital image is an array of pixels, where each pixel h

Datamodels, explain thee diffrent types of data models

explain thee diffrent types of data models

What are the key features of oracle, What are the key features of Oracle? ...

What are the key features of Oracle? Key features of Oracle are as follows: • Read Consistency • Concurrency • Locking Mechanisms • Quiesce Database • RAC • Portability

Data handling and research methods, Data Handling and Research Methods: ...

Data Handling and Research Methods: The dataset encompassing 130 participants contains several variables measuring detrimental health related behaviours referring to the use o

What is substitutability, What is substitutability? Any method of a cla...

What is substitutability? Any method of a class-say A can equally well be adjured with any object belonging to any subclasses B of A. This characteristic leads to code reuse, a

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

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