Relation instance or relation state, Database Management System

Assignment Help:

A relation instance indicates as r is a collection of tuples for a given relational schema at a exact point of time.

A relation state r of the relation schema R (A1,A2,..........AN), also denoted by r(R) is a set of n-tuples

r = {t1,t2,............tm}

Where each n-tuple is an ordered list of n values

t  =  1,v2,........, vn>

where every vi belongs to domain (Ai) or includes null values.

The relation schema is also known as  'intension' and relation state is also known as 'Extension'.


Related Discussions:- Relation instance or relation state

What is the candidate key for a table with columns, For problems 1-4, give ...

For problems 1-4, give all candidate keys for the tables with FDs specified.  Composite candidate keys must be put in parentheses, and candidate keys must be separated with commas

What does the cardinality ratio specify, What does the cardinality ratio sp...

What does the cardinality ratio specify? Mapping cardinalities or cardinality ratios state the number of entities to which another entity can be associated. Mapping cardinaliti

Difference between functions along with or without grouping, Explain the di...

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

What are the three types of data sources, What are the three types of data ...

What are the three types of data sources used with ODBC? An ODBC file data source is a file that can be shared between database users. An ODBC system data source is one that is

To delete a particular column in a relation which command, To delete a part...

To delete a particular column in a relation which command is used ? To delete a particular column in a relation ALTER command is used.

RAID technology, what characterizes the levels in RAID technology

what characterizes the levels in RAID technology

Explain mechanism of nested queries, Explain mechanism of nested queries? ...

Explain mechanism of nested queries? SQL gives a mechanism for nesting subqueries. A subquery is a select from where expression that is nested within one more query. A common u

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

Set difference, Set Difference If R1 and R2 are two union compatible re...

Set Difference If R1 and R2 are two union compatible relations or relations then result of R3 =R1- R2 is the relation that have only those tuples that are in R1 but not in R2.

Explain the function of object model, Explain the function of Object model ...

Explain the function of Object model Object model describes the classes of objects in system, including their attributes and operations which they support. The analysis object

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