Computer Science 1032A/B Lecture Notes - Lecture 2: Foreign Key, Relational Database, Cardinality

• School: Western University
• Department: Computer Science
• Course: Computer Science 1032A/B
• Professor: Louis Magguilli

Document Summary

A collection of data used for storing and grouping. Relational database: groups of data are related to each other in a meaningful way. A database: self-describing collection of integrated records. Relationships among records: values in one table relating to rows in other tables. Necessary to uniquely identify the instance of each entity. Databases using tables, primary keys, and foreign keys. A relationship is the association between two or more entities and captures how the entities are related to each other. They have two descriptive facets: cardinality (one or many) and participation level (optional or mandatory). Cardinality indicates the number of instances of the entities that are involved in the relationship. Not the total number of instances in the entity. Relationship to exist- professor is the chair of the department. Relationship is: can be chair of one and only one department, each department can have only one chair. (1:1 relationship = cardinality)