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Achieving the BCNF by Decomposition (2)  Three possible decompositions for relation TEACH 1. {student, instructor} and {student, course} 2. {course, instructor } and {course, student} 3. {instructor, course } and {instructor, student}  All three decompositions will lose fd1. We have to settle for sacrificing the functional dependency preser...

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Summary (continued)  A database may be accessed via an interactive database  Most often, however, data in a database is manipulate via application programs  Several methods of database programming: – embedded SQL – dynamic SQL – stored procedure and function

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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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 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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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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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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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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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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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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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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