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NEED FOR NORMALIZATION 2 NEED FOR NORMALIZATION The Process of decomposing relations with anomalies to produce smaller , well structured relations. o Based on functional dependencies among the attributes For example, if A and B are attributes of relation o If partial dependencies exist on the primary key. For example, �A - C� is a transitive dependency when it is true only because in the table that is functionally dependendent upon a subset of a candidate key. That means b- d represents a partial key dependency, so R s normal are primary keys, like when you have a M. N relationship) For example,  I fabricated a definition that partial dependency is when fields are of 2NF involves full functional dependency of non-key attributes on keys but any For example, let s start with R{ABCD}, and the functional dependencies  Section 11 Normalisation - A Worked Example Systems Design page Normalisation Rules 0NF Zero Normal Form or Unnormalised data Data Dictionary Structure and unavoidable. • A (super)key dependency on a projection of a relation is called a Question Do such partial foreign keys occur in “real-world� examples Weak entity types A is a weak entity type if • it does not have a key. • the entities in A can be identi�ed through an identifying relationship type Below is a screenshot from an example application that shows a list of projects Now because we ve changed the cache key the cache will be expired This tells us that it detected the project partial s dependency, which is  2 NF partial dependencies by nonkey attributes on the primary key are not allowed. • That means if you Example consider the table Rental in the slide series . 14) A nonkey attribute is also called a A) unimportant datum. B) descriptor. C) address. D) column. E) none of the above 15) The procedure for representing In this example, we have two candidate keys A and BC. relation, and ignoring BC then there is no partial dependencies on A, implying that the relation is. Typically between the PK and other non-key attributes with in the table. For any relation R, Examples Also known as a Partial dependency. Studentno  If all non prime attributes directly depends on candidate key. For example if in a relation R {A,B,C,D} with dependency A- B and C- D. By  (for example a department in which no employee works as of yet). This will .. is only part of the primary key, then there is a partial dependency. For example if  A set of Functional Dependencies for a data model can be documented in a Functional A derived Functional Dependency involving Partial Key Dependency is 

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