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Right and left outer joins are functionally equivalent. Neither provides any functionality that the other does not, so right and left outer joins may replace each other as long as the table order is switched. A Venn diagram representing the full join SQL statement between tables A and B.
Diagrama de Venn representando el Left Join, entre las tablas A y B, de una sentencia SQL como: Select (lista de campos) From A Left Join B On A.Key = B.Key.
A Venn diagram is a widely used diagram style that shows the logical relation between sets, popularized by John Venn (1834–1923) in the 1880s. The diagrams are used to teach elementary set theory, and to illustrate simple set relationships in probability, logic, statistics, linguistics and computer science.
Join and meet are dual to one another with respect to order inversion. A partially ordered set in which all pairs have a join is a join-semilattice. Dually, a partially ordered set in which all pairs have a meet is a meet-semilattice. A partially ordered set that is both a join-semilattice and a meet-semilattice is a lattice.
In set theory the Venn diagrams tell, that there is an element in one of the red intersections. (The existential quantifications for the red intersections are combined by or. They can be combined by the exclusive or as well.) Relations like subset and implication, arranged in the same kind of matrix as above. In set theory the Venn diagrams tell,
Venn diagram of information theoretic measures for three variables x, y, and z. Each circle represents an individual entropy: is the lower left circle, the lower right, and is the upper circle.
In commemoration of the 180th anniversary of Venn's birth, on 4 August 2014, Google replaced its normal logo on global search pages with an interactive and animated Google Doodle that incorporated the use of a Venn diagram. [24] [25] Venn Street in Clapham, London, which was the home of his grandfather, shows a Venn diagram on the street sign. [26]
R-diagrams can be used to easily simplify complicated logical expressions, using a step-by-step process. Using order of operations, logical operators are applied to R-diagrams in the proper sequence. Finally, the result is an R-diagram that can be converted back into a simpler logical expression. For example, take the following expression: