Xem 1-20 trên 864 kết quả Relational model
  • Bài giảng "Hệ cơ sở dữ liệu - Chương 4: Mô hình quan hệ - Relational model" trình bày các nội dung: Các định nghĩa cơ bản, các quy luật bảo toàn dữ liệu, các ngôn ngữ quan hệ, khung nhìn, hệ quản trị cơ sở dữ liệu quan hệ. Mời các bạn cùng tham khảo.

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  • Quan hệ (relation) là một bảng dữ liệu hai chiều gồm nhiều hàng (mẫu tin hay bản ghi) và nhiều cột (thuộc tính hoặc vùng tin). Mỗi cột tương ứng với một thuộc tính của thực thể. Mỗi dòng chứa các giá trị dữ liệu của một đối tượng cụ thể thuộc thực thể.

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  • The relational Model of Data is based on the concept of a Relation. A Relation is a mathematical concept based on the ideas of sets. The strength of the relational approach to data management comes from the formal foundation provided by the theory of relations. We review the essentials of the relational approach in this chapter.

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  • Database System: Chapter 2 - The Relational Data Model & SQL includes about Relational Model Concepts, Relational Model Constraints and Relational Database Schemas, Update Operations and Dealing with Constraint Violations, Basic SQL.

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  • Chapter 5 - The Relational Data Model and Relational Database Constraints present contents as: Relational model concepts, relational model constraints and relational database schemas, update operations and dealing with constraint violations.

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  • In this chapter, The contents concentrate on describing the basic principles of the relational model of data, begin by defining the modeling concepts and notation of the relational model, discussion of relational constraints that are considered an important part of the relational model and are automatically enforced in most relational DBMSs, defines the update operations of the relational model,...

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  • In this chapter we discuss the two formal languages for the relational model: the relational algebra and the relational calculus. The main contents in this chapter include: Example database application (COMPANY), overview of the QBE language (appendix D),...

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  • Chapter 2 presents the entity-relationship model. This model provides a high-level view of the issues in database design, and of the problems that we encounter in capturing the semantics of realistic applications within the constraints of a data model.

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  • The basic set of operations for the relational model is known as the relational algebra. These operations enable a user to specify basic retrieval requests. The result of a retrieval is a new relation, which may have been formed from one or more relations. The algebra operations thus produce new relations, which can be further manipulated using operations of the same algebra.

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  • This book introduces you to the theory of relational databases, focusing on the application of that theory to the design of computer languages that properly embrace it. The book is intended for those studying relational databases as part of a degree course in Information Technology (IT). Relational database theory, originally proposed by Edgar F. Codd in 1969, is a topic in Computer Science. Codd’s seminal paper (1970) was entitled A Relational Model of Data for Large Shared Data Banks (reference [5] in Appendix B)....

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  • Views are virtual tables. That means they should be updatable, just as "real" orare. In fact, view updatability isn’t just desirable, it’s crucial, for practical reasons as well as theoretical ones. But view updating has always been a controversial topic. Ever since the relational model first appeared, there has been widespread skepticism as to whether (in general) view updating is even possible.

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  • Information Extraction (IE) is a fundamental technology for NLP. Previous methods for IE were relying on co-occurrence relations, soft patterns and properties of the target (for example, syntactic role), which result in problems of handling paraphrasing and alignment of instances. Our system ARE (Anchor and Relation) is based on the dependency relation model and tackles these problems by unifying entities according to their dependency relations, which we found to provide more invariant relations between entities in many cases. ...

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  • Many methods are available for computing semantic similarity between individual words, but certain NLP tasks require the comparison of word pairs. This paper presents a kernel-based framework for application to relational reasoning tasks of this kind. The model presented here combines information about two distinct types of word pair similarity: lexical similarity and relational similarity.

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  • In this chapter, The contents concentrate on describing the basic principles of the relational model of data, begin by defining the modeling concepts and notation of the relational model, discussion of relational constraints that are considered an important part of the relational model and are automatically enforced in most relational DBMSs, defines the update operations of the relational model,...

    pdf8p kiepnaybinhyen_02 29-12-2015 4 1   Download

  • In this chapter we discuss the two formal languages for the relational model: the relational algebra and the relational calculus. The main contents in this chapter include: Example database application (COMPANY), overview of the QBE language (appendix D),... Inviting you to refer.

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  • Chapter 2 - The relational model. In this chapter students will be able to: Learn the conceptual foundation of the relational model, understand how relations differ from nonrelational tables, learn basic relational terminology, learn the meaning and importance of keys, foreign keys, and related terminology, understand how foreign keys represent relationships.

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  • Chapter 2 - Intro to relational model. Chapter 2 introduces the relational model of data, covering basic concepts such as the structure of relational databases, database schemas, keys, schema diagrams, relational query languages, and relational operations.

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  • The UML can be used to describe the complete development of relational and object relational databases 1 from business requirements through the physical data model. However, modeling of the physical data model must express a detailed description of the database. This is done using Rational’s Data Modeling Profile for the UML2 .

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  • Traditional Supply Chain Management (SCM) aims at movement of goods and services from one end of this chain to the other through different stages so as to improve the efficiency, productivity and profitability of the entire process. As SCM spans across the economic functions of the entire value chain of a product or service, it is vital for a company to join in, form, or coordinate its business related supply chains, forming various kinds of business relationships.

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  • Mô hình CSDL là phương thức biểu diễn các dữ liệu, giúp cho việc tổ chức các dữ liệu thuận tiện cho việc thiết kế, lưu trữ, xử lý Mô hình CSDL dùng mô hình toán học để mô tả CSDL dựa trên các tập hợp và phép toán Các mô hình CSDL phổ biến: Mô hình phân lớp (hierarchical model) Mô hình mạng (network model) Mô hình quan hệ (relational model) Mô hình thực thể-liên kết (entity-relationship model) Mô hình hướng đối tượng (object model) Mô hình XML – bán cấu trúc (semi-stru...

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