Lecture 3 - Relational Model.ppt - Introduction to Database...

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IS 230 Lecture 3 – The Relational Model Slide 1 Chapter 3 The Relational Model Introduction to Database Systems IS 230 This is the instructor’s notes and student has to read the textbook for complete material. Dr. Abdulrahman Alothaim
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IS 230 Lecture 3 – The Relational Model Slide 2 Lecture Outline The Relational Data Model and Relational Database Constraints Relational Model Constraints and Relational Database Schemas Update Operations, Transactions, and Dealing with Constraint Violations
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IS 230 Lecture 3 – The Relational Model Slide 3 The Relational Data Model and Relational Database Constraints Relational model First commercial implementations available in early 1980s Has been implemented in a large number of commercial system Hierarchical and network models Preceded the relational model
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IS 230 Lecture 3 – The Relational Model Slide 4 Relational Model Concepts Represents data as a collection of relations Table of values Row Represents a collection of related data values Fact that typically corresponds to a real-world entity or relationship Tuple Table name and column names Interpret the meaning of the values in each row attribute
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IS 230 Lecture 3 – The Relational Model Slide 5 Relational Model Concepts (cont’d.)
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IS 230 Lecture 3 – The Relational Model Slide 6 Definition Summary Informal Terms Formal Terms Table Relation Column Header Attribute All possible Column Values Domain Row Tuple Table Definition Schema of a Relation Populated Table State of the Relation
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IS 230 Lecture 3 – The Relational Model Slide 7 Domains, Attributes, Tuples, and Relations Domain D Set of atomic values Atomic Each value indivisible Specifying a domain Data type specified for each domain
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IS 230 Lecture 3 – The Relational Model Slide 8 Domains, Attributes, Tuples, and Relations (cont’d.) Relation schema R Denoted by R ( A 1 , A 2 , ..., A n ) Made up of a relation name R and a list of attributes, A 1 , A 2 , ..., A n Attribute A i Name of a role played by some domain D in the relation schema R Degree (or arity ) of a relation Number of attributes n of its relation schema
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IS 230 Lecture 3 – The Relational Model Slide 9 Domains, Attributes, Tuples, and Relations (cont’d.) Relation (or relation state ) Set of n -tuples r = { t 1 , t 2 , ..., t m } Each n -tuple t Ordered list of n values t =<v 1 , v 2 , ..., v n > Each value v i , 1 ≤ i ≤ n , is an element of dom( A i ) or is a special NULL value
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IS 230 Lecture 3 – The Relational Model Slide 10 Domains, Attributes, Tuples, and Relations (cont’d.) Cardinality Total number of values in domain Current relation state Relation state at a given time
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