關(guān)系模式算法設計

畢業(yè)論文

摘  要

數據庫技術(shù)是計算機科學(xué)中發(fā)展最快的領(lǐng)域之1，也是應用最廣的技術(shù)之1，它已成為計算機信息系統與應用系統的核心技術(shù)和重要基礎。數據庫設計是數據庫應用系統設計的重要步驟,數據庫是否適合應用系統的設計是至關(guān)重要的，為了使數據庫設計方法走向完備，人們研究了規范化理論，主要通過(guò)討論1個(gè)關(guān)系屬性間不同的依賴(lài)情況，討論如何根據屬性間依賴(lài)情況來(lái)判定關(guān)系是否具有某些不合適的性質(zhì)，關(guān)系數據中的關(guān)系是要滿(mǎn)足1定要求的，滿(mǎn)足不同程度要求的為不同范式。本文討論的是給出1個(gè)范式，判定是那1種范式。 本文在函數依賴(lài)的范疇內對關(guān)系模型的規范化理論及其運用問(wèn)題進(jìn)行了探討，對2NF,3NF,BCNF范式進(jìn)行了研究，實(shí)現了上面3種范式的自動(dòng)生成算法，簡(jiǎn)化了范式的判定難度。系統地提出1整套使用地關(guān)系規范化地具體方法和步驟，給出了1個(gè)判定關(guān)系模式是否屬于其中1種的算法。根據本文提供的方法可以容易判斷1個(gè)關(guān)系模式，從而避免了因為數據庫設計不當而對數據庫管理系統造成的影響。
關(guān)鍵字：函數依賴(lài)；候選關(guān)鍵字；閉包；傳遞依賴(lài)。

Abstract

The technology of the database is one of the fields with the fastest developing speed in computer science, using one of the widest technology too, it has already become information system of the computer and the key technology of the application system and important foundation. Data design of storehouse whether database use important step that system design, database suitable for design of application system essential, in order to make the database design method move towards being complete, people have studied the standardized theory, one relation different reliance situation under attribute through discussion, discuss how rely on situation is it judge according to attribute relation have some improper nature to come mainly, concern relation of data to meet certain demand ,meet demand in various degree different normal form. What this text discussed is to provide a normal form ,judge which is it Normal form.Within the category of function dependency，the theory and application of normalization of relation model are studied. a set of practically specific methods of relation normalization are systematically put forward. To the 2NF, 3NF,the type of BCNF carried on a research, carrying out a top is three kinds of calculate ways with automatically born modeltypes, simplified the model type to judge a difficulty. And a polynom ial time algorithm to decide whether a relation model is in them given. And provide a arithmetic of determinant a relation pattern is or not pertain to bcnf. Using the way of this artrcle we can easy judge a relation mode, accordingly avoid the influence of unsuitable designing database.
Keywords : Function relies on ;  Candidate key word ; closure ; Transmit and rely on.

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