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Primary key and foreign key relationships

Primary key and foreign key relationships

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Primary key and foreign key relationships

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  1. Primary key and foreign key relationships IST359 M005 Yang Wang ywang@syr.edu 342 Hinds http://blackboard.syr.edu

  2. Cardinality • 1-1 relationship • 1-many relationship • Many-many relationship

  3. 1-1 relationship • Students table • student_id (primary key) • student_ssn (foreign key) • SSNs table • ssn (primary key) Students (student_ssn) references to SSNs (ssn) 1 student has only 1 SSN

  4. 1-many relationship

  5. Many-many relationship This M-M Relationship has been resolved into two 1-M relationships