• Bài giảng Database Systems - Chapter 8 SQL-99: Schema Definition, Basic Constraints, and QueriesBài giảng Database Systems - Chapter 8 SQL-99: Schema Definition, Basic Constraints, and Queries

    UPDATE  Used to modify attribute values of one or more selected tuples  A WHERE-clause selects the tuples to be modified  An additional SET-clause specifies the attributes to be modified and their new values  Each command modifies tuples in the same relation  Referential integrity should be enforced

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  • Bài giảng Database Systems - Chapter 7 Relational Database Design by ER- And EERR-to-Relational MappingBài giảng Database Systems - Chapter 7 Relational Database Design by ER- And EERR-to-Relational Mapping

     Step 9: Mapping of Union Types (Categories). – For mapping a category whose defining superclass have different keys, it is customary to specify a new key attribute, called a surrogate key, when creating a relation to correspond to the category. – In the example below we can create a relation OWNER to correspond to the OWNER category and incl...

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  • Bài giảng Database Systems - Chapter 06 The Relational Algebra and CalculusBài giảng Database Systems - Chapter 06 The Relational Algebra and Calculus

    QBE Examples Specifying complex cinditions in QBE:  A technique called the “condition box” is used in QBE to state more involved Boolean expressions as conditions.  The D.4(a) gives employees who work on either project 1 or 2, whereas the query in D.4(b) gives those who work on both the projects.

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  • Bài giảng Database Systems - Chapter 05 The Relational Data Model and Relational Database ConstraintsBài giảng Database Systems - Chapter 05 The Relational Data Model and Relational Database Constraints

    In-Class Exercise (Taken from Exercise 5.15) Consider the following relations for a database that keeps track of student enrollment in courses and the books adopted for each course: STUDENT(SSN, Name, Major, Bdate) COURSE(Course#, Cname, Dept) ENROLL(SSN, Course#, Quarter, Grade) BOOK_ADOPTION(Course#, Quarter, Book_ISBN) TEXT(Book_ISBN, B...

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  • Bài giảng Database Systems - Chapter 4 - Part II Enhanced Entity-Relationship and UML ModelingBài giảng Database Systems - Chapter 4 - Part II Enhanced Entity-Relationship and UML Modeling

    Summary of Modeling Concepts ABSTRACTIONS  CLASSIFICATION  AGGREGATION (COMPOSITION AND ASSOCIATION)  IDENTIFICATION  GENERALIZATION AND SPECIALIZATION CONSTRAINTS  CARDINALITY (Min. and Max)  PARTICIPATION  COVERAGE (Total vs. Partial, Exclusive vs. Overlapping)

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  • Bài giảng Database Systems - Chapter 4 - Part I Enhanced Entity-Relationship and UML ModelingBài giảng Database Systems - Chapter 4 - Part I Enhanced Entity-Relationship and UML Modeling

    Formal Definitions of EER Model (2)  Subclass S of C is predicate defined if predicate p on attributes of C is used to specify membership in S; that is, S = C[p], where C[p] is the set of entities in C that satisfy p  A subclass not defined by a predicate is called user-defined  Attribute-defined specialization: if a predicate A = ci (where...

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  • Bài giảng Database Systems - Chapter 3 Data Modeling Using the Entity-Relationship (ER) ModelBài giảng Database Systems - Chapter 3 Data Modeling Using the Entity-Relationship (ER) Model

    Extended Entity-Relationship (EER) Model  Incorporates Set-subset relationships  Incorporates Specialization/Generalization Hierarchies NEXT CHAPTER ILLUSTRATES HOW THE ER MODEL CAN BE EXTENDED WITH - Set-subset relationships and Specialization/Generalization Hierarchies and how to display them in EER diagrams

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  • Bài giảng Database Systems - Chapter 02 Database System Concepts and ArchitectureBài giảng Database Systems - Chapter 02 Database System Concepts and Architecture

    Classification of DBMSs Distributed Database Systems have now come to be known as client server based database systems because they do not support a totally distributed environment, but rather a set of database servers supporting a set of clients

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  • Bài giảng Database Systems - Chapter 1 Introduction and Conceptual ModelingBài giảng Database Systems - Chapter 1 Introduction and Conceptual Modeling

    When not to use a DBMS When no DBMS may suffice: – If the database system is not able to handle the complexity of data because of modeling limitations – If the database users need special operations not supported by the DBMS.

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  • Môn thi Phân tích và thiết kế hệ thống thông tinMôn thi Phân tích và thiết kế hệ thống thông tin

    Yêu cầu : 1. Xây dựng mô hình thực thể  kết hợp (EAM) cho bài toán trên. Tự ấn định số lượng và tên các thuộc tính của mỗi thực thể tương ứng. 2. Chuyển EAM về mô hình logic dữ liệu dạng bảng hoặc lược đồ quan hệ 3. Mô tả các tệp CSDL và các quan hệ giữa chúng (nếu có), chỉ ra các tệp chủ (master), tệp phục vụ (slave) và các khoá sắp xếp tư...

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