Normalization Tutorial

Normalization Tutorial - Normalization Validity Check on...

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Validity Check on the Data Structures Normalization
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Normalization TIP: Correct ERD’s produce tables in 3NF (or very close)! Process consisting of a series of tests that provide a final check on the validity of our data structures. .. Goal is to reduce data redundancy that causes problems called anomalies . . . Anomalies occur when we incorrectly combine attributes into relations. Looking for dependencies between attributes.
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Important Concepts Functional Dependency : An association between attributes of an entity such that the value of one attribute determines the value of another attribute. As a general rule, we want to have a dependency between the primary key and all other attributes, but we do not want to have dependencies between non-key attributes.
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st Normal Form (1NF ) Definition: Must be a relation. Translation: Must not have any repeating groups of attributes—i.e., attributes or groups of attributes that have multiple values for one instance of the entity. Method(1): “Back to the ERD method”—For any multivalued attribute (or group of attributes), add an entity to the ERD and model the relationship between new entity and existing entity as one-many or many-many. Examine other attributes to determine if attributes apply to multivalued attribute or stay in original structure. For example, Student with multiple majors would become Student and Major entities with many to many relationship (Student has many Majors and a Major can be had by many Students). Method (2): In some cases, multivalued attributes can be divided into two or more separate attributes. (e.g., HomePhone, WorkPhone, etc.) This should be considered carefully since it can cause problems in retrieving data. (e.g.,
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Normalization Tutorial - Normalization Validity Check on...

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