lecture-12-relational-model

lecture-12-relational-model - The Relational Model T. M....

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Unformatted text preview: The Relational Model T. M. Murali October 4, 2010 T. M. Murali October 4, 2010 CS 4604: The Relational Model Course Outline I Weeks 15, 13: Query/Manipulation Languages I The relational model I Relational Algebra I SQL I Data definition I Programming with SQL I Weeks 68: Data Modelling I Entity-Relationship (E/R) approach I Good E/R design I Specifying Constraints I Converting E/R model to relational model. E/R design Relational schema Relational DBMS Ideas T. M. Murali October 4, 2010 CS 4604: The Relational Model Course Outline I Weeks 15, 13: Query/Manipulation Languages I The relational model I Relational Algebra I SQL I Data definition I Programming with SQL I Weeks 68: Data Modelling I Entity-Relationship (E/R) approach I Good E/R design I Specifying Constraints I Converting E/R model to relational model. E/R design Relational schema Relational DBMS Ideas T. M. Murali October 4, 2010 CS 4604: The Relational Model The Relational Model I Built around a single concept for modelling data: the relation or table. I Supports high-level programming language (SQL). I Has an elegant mathematical design theory. I Most current DBMS are relational. T. M. Murali October 4, 2010 CS 4604: The Relational Model The Relation I A relation is a two-dimensional table: I Relation table. I Attribute column name. I Tuple row (not the header row). I Database collection of relations. CoursesTaken Student Course Grade Hermione Grainger Potions A- Draco Malfoy Potions B Harry Potter Potions A Ron Weasley Potions C T. M. Murali October 4, 2010 CS 4604: The Relational Model The Schema CoursesTaken Student Course Grade Hermione Grainger Potions A- Draco Malfoy Potions B Harry Potter Potions A Ron Weasley Potions C I The schema of a relation is the name of the relation followed by a paranthetised list of attributes. CoursesTaken(Student, Course, Grade) I A design in a relational model consists of a set of schemas. I Such a set of schemas is called a relational database schema . T. M. Murali October 4, 2010 CS 4604: The Relational Model Converting E/R Diagrams to Relational Designs I Entity set relation. I Attribute of an entity set attribute of a relation. I Relationship relation whose attributes are I Attribute of the relationship itself. I Key attributes of the connected entity sets. I Several special cases: I Weak entity sets. I Combining relations (especially for many-one relationships). I Isa relationships and subclasses. T. M. Murali October 4, 2010 CS 4604: The Relational Model Example for Conversion Courses Students Professors Take Teach Name Address Number Office Name Age Departments Offer Classroom Name Name Enrollment Evaluation Grade T. M. Murali October 4, 2010 CS 4604: The Relational Model Schemas for Non-Weak Entity Sets Courses Students Professors Take Teach Name Address Number Office Name Age Departments Offer Classroom Name Name Enrollment Evaluation Grade I For each entity set, create a relation with the same name and with the same set of attributes....
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lecture-12-relational-model - The Relational Model T. M....

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