In relational algebra, a selection (sometimes called a restriction to avoid confusion with SQL's use of SELECT) is a unary operation written as
or where:
The selection selects all those tuples in for which holds between the and the attribute.
The selection selects all those tuples in for which holds between the attribute and the value .
For an example, consider the following tables where the first table gives the relation , the second table gives the result of and the third table gives the result of .
More formally the semantics of the selection is defined as
follows:
The result of the selection is only defined if the attribute names that it mentions are in the heading of the relation that it operates upon.
In computer languages it is expected that any truth-valued expression be permitted as the selection condition rather than restricting it to be a simple comparison.
Relational algebra, first described by E.F. Codd while at IBM, is a family of algebras with a well-founded semantics used for modelling the data stored in relational databases, and defining queries on it.
The main application of relational algebra is providing a theoretical foundation for relational databases, particularly query languages for such databases, chief among which is SQL.
Introduction
Relational algebra received little attention outside of pure mathematics until the publication of E.F. Codd's relational model of data in 1970. Codd proposed such an algebra as a basis for database query languages. (See section Implementations.)
Relational Investors, an activist investment fund based in San Diego, California
Computing
Relational calculus, part of the relational model for databases that provides a declarative way to specify database queries
Relational database, a database that has a collection of tables of data items, all of which is formally described and organized according to the relational model
In Relational Grammar, constituents that serve as the arguments to predicates are numbered. This numbering system corresponds loosely to the notions of subject, direct object and indirect object. The numbering scheme is subject → (1), direct object → (2) and indirect object → (3). A schematic representation of a clause in this formalism might look like:
Other Features
Strata
Chomage
Predicate valence
Universals
One of the components of RG theory is a set of linguistic universals stated in terms of the numbered roles presented above. Such a universal is the Stratal Uniqueness Law which states that there can be "at most one 1, 2, and 3 per stratum.
Further reading
Blake, Barry J. (1990). Relational grammar. London: Routledge.
Death Note is a 37-episode anime series based on the manga series of the same title written by Tsugumi Ohba and illustrated by Takeshi Obata. Death Note aired in Japan on the Nippon Television (NTV) network every Tuesday, from October 3, 2006, to June 26, 2007. The plot of the series primarily revolves around high school student Light Yagami, who decides to rid the world of evil with the help of a supernatural notebook titled Death Note. This book causes the death of anyone whose name is written in it and is passed on to Light by the God of Death (or Shinigami) Ryuk after he becomes bored within the Shinigami world.
A three-hour "Director's Cut" compilation TV special, titled "Death Note: Relight: Visions of a God", aired on NTV a few months after the anime concluded. Although advertised to be the "complete conclusion", the popularity of the series inspired the release of a second TV special, titled "Death Note: Relight 2: L's Successors" nearly a year later. These specials recap the first and second arcs of the anime respectively, with new scenes added to fill in any plot holes resulted from omitted footage.
Selection referred to "free selection before survey" of crown land in some Australian colonies under land legislation introduced in the 1860s. These acts were similar to the United StatesHomestead Act and were intended to encourage closer settlement, based on intensive agriculture, such as wheat-growing, rather than extensive agriculture, such as wool production. Selectors often came into conflict with squatters, who already occupied the land and often managed to circumvent the law.
New South Wales
The Robertson Land Acts allowed those with limited means to acquire land. With the stated intention of encouraging closer settlement and fairer allocation of land by allowing 'free selection before survey', the Land Acts legislation was passed in 1861. The relevant acts were named the Crown Lands Alienation Act and Crown Lands Occupation Act. The application of the legislation was delayed until 1866 in inland areas such as the Riverina where existing squatting leases were still to run their course. In any case severe drought in the Riverina in the late 1860s initially discouraged selection in areas except those close to established townships. Selection activity increased with more favourable seasons in the early 1870s.
DBMS: Basics of Relational Algebra
Topics discussed:
1. Introduction to relational algebra with an explanation of application areas of abstract algebra, linear algebra, and boolean algebra.
2. Theoretical basics of relational algebra.
3. Importance of having relational algebra in relational databases.
4. List of various fundamental and additional operations in relational algebra.
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published: 28 Oct 2022
Relational Algebra Operations - Unary
DBMS: Relational Algebra Operations - Unary
Topics discussed:
1. The SELECTION Operation.
2. The PROJECTION Operation.
3. The RENAME Operation.
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published: 05 Aug 2021
05-01-relational-algebra-1.mp4
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published: 04 Jan 2013
Relational Algebra Operations - Binary
DBMS: Relational Algebra Operations - Binary
Topics discussed:
1. The JOIN Operation.
2. The THETA JOIN.
3. The EQUIJOIN Operation.
4. The NATURAL JOIN Operation.
5. The DIVISION Operation.
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published: 30 Aug 2021
Relational Algebra (Select Operation)
DBMS: Relational Algebra (Select Operation)
Topics discussed:
1. Recap of various fundamental operations in relational algebra.
2. Basics of Select (σ) operation in relational algebra.
3. Syntax of Select (σ) operation in relational algebra.
4. Difference between select (σ) and project (π) in relational algebra.
5. Solved examples using select (σ) in relational algebra.
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published: 31 Oct 2022
relational algebra operations in dbms
relational algebra operations like projection,cross product, set -difference
published: 13 Mar 2018
DBMS - Relational Algebra Questions with Solution - Part 1.
We solve a question related to Relational Algebra(DBMS ).
For SQL(MySQL) Solution for the same question, click here: https://youtu.be/ca3d5Lv1arI
published: 16 Mar 2021
01 - Relational Model & Relational Algebra (CMU Intro to Database Systems / Fall 2022)
Andy Pavlo (https://www.cs.cmu.edu/~pavlo/)
Slides: https://15445.courses.cs.cmu.edu/fall2022/slides/01-introduction.pdf
Notes https://15445.courses.cs.cmu.edu/fall2022/notes/01-introduction.pdf
15-445/645 Intro to Database Systems (Fall 2022)
Carnegie Mellon University
https://15445.courses.cs.cmu.edu/fall2022/
published: 31 Aug 2022
Relational Algebra Exercises
published: 08 Jun 2014
Relational Algebra Queries (Part 1)
DBMS: Relational Algebra Queries (Part 1)
Topics discussed:
Solved queries based on Relational Algebra:
1) Retrieve the names of all employees who work for the ‘Headquarters’ Department.
2) For every project located in ‘Stafford’, list the project number, controlling department, and the manager’s name.
3) Find the names of the employees who work on all the projects controlled by DNo = 3.
4) Make a list of project numbers for projects that involve an employee with LName = ‘Smith’, either as a worker or as a manager of the department that controls the project.
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DBMS: Basics of Relational Algebra
Topics discussed:
1. Introduction to relational algebra with an explanation of application areas of abstract algebra, linear ...
DBMS: Basics of Relational Algebra
Topics discussed:
1. Introduction to relational algebra with an explanation of application areas of abstract algebra, linear algebra, and boolean algebra.
2. Theoretical basics of relational algebra.
3. Importance of having relational algebra in relational databases.
4. List of various fundamental and additional operations in relational algebra.
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Music:
Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebra
DBMS: Basics of Relational Algebra
Topics discussed:
1. Introduction to relational algebra with an explanation of application areas of abstract algebra, linear algebra, and boolean algebra.
2. Theoretical basics of relational algebra.
3. Importance of having relational algebra in relational databases.
4. List of various fundamental and additional operations in relational algebra.
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Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebra
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DBMS: Relational Algebra (Select Operation)
Topics discussed:
1. Recap of various fundamental operations in relational algebra.
2. Basics of Select (σ) operatio...
DBMS: Relational Algebra (Select Operation)
Topics discussed:
1. Recap of various fundamental operations in relational algebra.
2. Basics of Select (σ) operation in relational algebra.
3. Syntax of Select (σ) operation in relational algebra.
4. Difference between select (σ) and project (π) in relational algebra.
5. Solved examples using select (σ) in relational algebra.
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Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebraOperations
DBMS: Relational Algebra (Select Operation)
Topics discussed:
1. Recap of various fundamental operations in relational algebra.
2. Basics of Select (σ) operation in relational algebra.
3. Syntax of Select (σ) operation in relational algebra.
4. Difference between select (σ) and project (π) in relational algebra.
5. Solved examples using select (σ) in relational algebra.
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Music:
Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebraOperations
Andy Pavlo (https://www.cs.cmu.edu/~pavlo/)
Slides: https://15445.courses.cs.cmu.edu/fall2022/slides/01-introduction.pdf
Notes https://15445.courses.cs.cmu.edu/...
Andy Pavlo (https://www.cs.cmu.edu/~pavlo/)
Slides: https://15445.courses.cs.cmu.edu/fall2022/slides/01-introduction.pdf
Notes https://15445.courses.cs.cmu.edu/fall2022/notes/01-introduction.pdf
15-445/645 Intro to Database Systems (Fall 2022)
Carnegie Mellon University
https://15445.courses.cs.cmu.edu/fall2022/
Andy Pavlo (https://www.cs.cmu.edu/~pavlo/)
Slides: https://15445.courses.cs.cmu.edu/fall2022/slides/01-introduction.pdf
Notes https://15445.courses.cs.cmu.edu/fall2022/notes/01-introduction.pdf
15-445/645 Intro to Database Systems (Fall 2022)
Carnegie Mellon University
https://15445.courses.cs.cmu.edu/fall2022/
DBMS: Relational Algebra Queries (Part 1)
Topics discussed:
Solved queries based on Relational Algebra:
1) Retrieve the names of all employees who work for the ...
DBMS: Relational Algebra Queries (Part 1)
Topics discussed:
Solved queries based on Relational Algebra:
1) Retrieve the names of all employees who work for the ‘Headquarters’ Department.
2) For every project located in ‘Stafford’, list the project number, controlling department, and the manager’s name.
3) Find the names of the employees who work on all the projects controlled by DNo = 3.
4) Make a list of project numbers for projects that involve an employee with LName = ‘Smith’, either as a worker or as a manager of the department that controls the project.
Follow Neso Academy on Instagram: @nesoacademy(https://bit.ly/2XP63OE)
Contribute: https://www.nesoacademy.org/donate
Memberships: https://bit.ly/2U7YSPI
Books: https://www.nesoacademy.org/recommended-books
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Facebook ► https://goo.gl/Nt0PmB
Twitter ► https://twitter.com/nesoacademy
Music:
Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebraQueries
DBMS: Relational Algebra Queries (Part 1)
Topics discussed:
Solved queries based on Relational Algebra:
1) Retrieve the names of all employees who work for the ‘Headquarters’ Department.
2) For every project located in ‘Stafford’, list the project number, controlling department, and the manager’s name.
3) Find the names of the employees who work on all the projects controlled by DNo = 3.
4) Make a list of project numbers for projects that involve an employee with LName = ‘Smith’, either as a worker or as a manager of the department that controls the project.
Follow Neso Academy on Instagram: @nesoacademy(https://bit.ly/2XP63OE)
Contribute: https://www.nesoacademy.org/donate
Memberships: https://bit.ly/2U7YSPI
Books: https://www.nesoacademy.org/recommended-books
Website ► https://www.nesoacademy.org/
Forum ► https://forum.nesoacademy.org/
Facebook ► https://goo.gl/Nt0PmB
Twitter ► https://twitter.com/nesoacademy
Music:
Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebraQueries
DBMS: Basics of Relational Algebra
Topics discussed:
1. Introduction to relational algebra with an explanation of application areas of abstract algebra, linear algebra, and boolean algebra.
2. Theoretical basics of relational algebra.
3. Importance of having relational algebra in relational databases.
4. List of various fundamental and additional operations in relational algebra.
Follow Neso Academy on Instagram: @nesoacademy(https://bit.ly/2XP63OE)
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Music:
Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebra
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DBMS: Relational Algebra (Select Operation)
Topics discussed:
1. Recap of various fundamental operations in relational algebra.
2. Basics of Select (σ) operation in relational algebra.
3. Syntax of Select (σ) operation in relational algebra.
4. Difference between select (σ) and project (π) in relational algebra.
5. Solved examples using select (σ) in relational algebra.
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Music:
Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebraOperations
Andy Pavlo (https://www.cs.cmu.edu/~pavlo/)
Slides: https://15445.courses.cs.cmu.edu/fall2022/slides/01-introduction.pdf
Notes https://15445.courses.cs.cmu.edu/fall2022/notes/01-introduction.pdf
15-445/645 Intro to Database Systems (Fall 2022)
Carnegie Mellon University
https://15445.courses.cs.cmu.edu/fall2022/
DBMS: Relational Algebra Queries (Part 1)
Topics discussed:
Solved queries based on Relational Algebra:
1) Retrieve the names of all employees who work for the ‘Headquarters’ Department.
2) For every project located in ‘Stafford’, list the project number, controlling department, and the manager’s name.
3) Find the names of the employees who work on all the projects controlled by DNo = 3.
4) Make a list of project numbers for projects that involve an employee with LName = ‘Smith’, either as a worker or as a manager of the department that controls the project.
Follow Neso Academy on Instagram: @nesoacademy(https://bit.ly/2XP63OE)
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Books: https://www.nesoacademy.org/recommended-books
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Forum ► https://forum.nesoacademy.org/
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Music:
Axol x Alex Skrindo - You [NCS Release]
#DBMSByNeso #DBMS #RelationalAlgebraQueries
In relational algebra, a selection (sometimes called a restriction to avoid confusion with SQL's use of SELECT) is a unary operation written as
or where:
The selection selects all those tuples in for which holds between the and the attribute.
The selection selects all those tuples in for which holds between the attribute and the value .
For an example, consider the following tables where the first table gives the relation , the second table gives the result of and the third table gives the result of .
More formally the semantics of the selection is defined as
follows:
The result of the selection is only defined if the attribute names that it mentions are in the heading of the relation that it operates upon.
In computer languages it is expected that any truth-valued expression be permitted as the selection condition rather than restricting it to be a simple comparison.
This idea was formalized by William Hamilton in 1964, who captured the key evolutionary ideas of inclusive fitness and kin selection in a simple algebraic relationship ... algebraic relationship.