MISY330 Lecture Notes - Lecture 1: Unique Key, Ibm Db2, Rds-1
11 Oct 2018
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Repetition of: data (value, facts x this is the problem if it"s an entity instance. Composite key: any number of columns that make a record unique (associate table) What is entity-relationship (er) modeling: entity- relationship modeling: a formal method to help us convert english language business descriptions into normalized data in tabular format, most popular diagramming technique, many variations of er diagrams in use. No two entities can have the same value of primary key: example: ssn. What are relationships: relationship: an association between entities. Drawn as a line connecting entities involved: sometimes shown using a diamond shape, example: a salesperson sells products or products are sold by salespersons. Misy330 lecture notes: 32-year-old rebecca is working on projects #456 with her manager brown, rebecca works on the education analytics project, the number of hours rebecca worked is about 53. How to keep track of number of entity instances involved in a relationship.
