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

Key to represent relationship between tables is called, Key to represent re...

Key to represent relationship amongs tables is called ? A Key that represent the relationship between tables is called Foreign Key.

What is the difference between where and having clauses, What is the differ...

What is the difference between WHERE and HAVING clauses?. Predicates in the WHERE clause applies to every tuple while the predicate in the HAVING clause applies to groups.

Distributed query and transaction processing, a.  Construct a query around ...

a.  Construct a query around any one of the functional divisions you made in 4a such that if executed in the distributed design of 4 would require reconstruction of at least two ho

Give the levels of data abstraction, Give the levels of data abstraction? ...

Give the levels of data abstraction? There are three levels of Data Abstraction a) Physical level b) logical level c) view level

Generalization and specialization, design a generalization specialization h...

design a generalization specialization hierarchy for a motor vehicle sales company. the company sells motorcycles, passenger cars, vens and buses.

Data management, Develop a database broker framework to implement a persist...

Develop a database broker framework to implement a persistence mechanism for the domain objects involved in the use case dealt with in Question 2.  a. Specify the attribute type

DW, #ques Define a job scheduling strategy that will meet business requirem...

#ques Define a job scheduling strategy that will meet business requirement of reporting availability by 6am CST for the following cubes? Show the job scheduling dependencies in a p

Introduction to Database Design and Development, Every School has many teac...

Every School has many teachers and many students. Each student is assigned to one school and each teacher works for one school only. Each teacher teaches more than one subject but

Physical records, Physical Records These are the records that are store...

Physical Records These are the records that are stored in the secondary storage devices. For the database relation, physical records are the group of fields kept in adjacent me

Explain instance and schemas, Explain Instance and schemas? Instances ...

Explain Instance and schemas? Instances and schemas: Databases changes over time as the information is deleted and inserted. The collection of information stored in database

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