翻訳と辞書 Words near each other ・ Generation of Animals ・ Generation of binomial series using calculus ・ Generation of Chaos ・ Generalized Pochhammer symbol ・ Generalized Poincaré conjecture ・ Generalized polygon ・ Generalized processor sharing ・ Generalized Procrustes analysis ・ Generalized pustular psoriasis ・ Generalized quadrangle ・ Generalized quantifier ・ Generalized randomized block design ・ Generalized relative entropy ・ Generalized Riemann hypothesis ・ Generalized second-price auction ・ Generalized selection ・ Generalized semi-infinite programming ・ Generalized signal averaging ・ Generalized singular value decomposition ・ Generalized spectrogram ・ Generalized star height problem ・ Generalized suffix tree ・ Generalized symmetric group ・ Generalized System of Preferences ・ Generalized taxicab number ・ Generalized Timing Formula ・ Generalized Tobit ・ Generalized tree alignment ・ Generalized trichoepithelioma ・ Generalized trigonometry Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Generalized selection ： ウィキペディア英語版 Generalized selection In relational algebra, a generalized selection is a unary operation written as $\backslash sigma\_\backslash varphi(R)$ where $\backslash varphi$ is a propositional formula that consists of atoms as allowed in the normal selection and the logical operators $\backslash and$ (and), $\backslash or$ (or) and $\backslash lnot$ (negation). This selection selects all those tuples in $R$ for which $\backslash varphi$ holds. For an example, consider the following tables where the first table gives the relation $Person$ and the second the result of $\backslash sigma\_(Person)$. | |} Formally the semantics of the generalized selection is defined as follows: : $\backslash sigma\_\backslash varphi(R)\; =\; \backslash$ The result of the selection is only defined if the attribute names that it mentions are in the header of the relation that it operates upon. The simulation of a generalized selection that is not a fundamental selection with the fundamental operators is defined by the following rules: : $\backslash sigma\_(R)\; =\; \backslash sigma\_\backslash varphi(R)\; \backslash cap\; \backslash sigma\_\backslash psi(R)$ : $\backslash sigma\_(R)\; =\; \backslash sigma\_\backslash varphi(R)\; \backslash cup\; \backslash sigma\_\backslash psi(R)$ : $\backslash sigma\_(R)\; =\; R\; -\; \backslash sigma\_\backslash varphi(R)$ The generalized selection is expressible with other basic algebraic operations. In SQL, general selections are performed by using WHERE definitions with AND, OR, or NOT operands in SELECT, UPDATE, and DELETE statements. ==See also== * Selection (relational algebra) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Generalized selection」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.