ITM 500 Lecture Notes - Lecture 8: Ticker Tape, Natural Key, Surrogate Key
2 Apr 2017
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Chapter 5 section 5. 3 entity integrity: The most important characteristic of an entity is its primary key, which uniquely identifies each instance. Its function is to guarantee entity integrity. They work together with foreign keys to implement relationships in the relational model. A natural key is a real-world, generally accepted identified used to uniquely identify real world objects (i. e. invoice #s to identify specific invoices) If an entity has a natural identifier, a data modeller uses it as the primary key of the entity being modeled. The identification and description are separate semantic constructs in the model. The function of the primary key is to guarantee entity integrity, not to describe the entity. Primary keys and foreign keys are used to implement relationships among entities. In the real world, when shopping at the grocery store, you select products by taking them and reading the labels, not by looking at the stock number.
