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12.1: Normal Form

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    Normalization should be part of the database design process. However, it is difficult to separate the normalization process from the ER modelling process so the two techniques should be used concurrently.

    Use an entity relation diagram (ERD) to provide the big picture, or macro view, of an organization’s data requirements and operations. This is created through an iterative process that involves identifying relevant entities, their attributes and their relationships.

    Normalization procedure focuses on characteristics of specific entities and represents the micro view of entities within the ERD.

    What Is Normalization?

    Normalization is the branch of relational theory that provides design insights. It is the process of determining how much redundancy exists in a table. The goals of normalization are to:

    • Be able to characterize the level of redundancy in a relational schema
    • Provide mechanisms for transforming schemas in order to remove redundancy

    Normalization theory draws heavily on the theory of functional dependencies. Normalization theory defines six normal forms (NF). Each normal form involves a set of dependency properties that a schema must satisfy and each normal form gives guarantees about the presence and/or absence of update anomalies. This means that higher normal forms have less redundancy, and as a result, fewer update problems.

    Normal Forms

    All the tables in any database can be in one of the normal forms we will discuss next.  Ideally we only want minimal redundancy for PK to FK. Everything else should be derived from other tables.  There are six normal forms, but we will only look at the first four, which are:

    • First normal form (1NF)
    • Second normal form (2NF)
    • Third normal form (3NF)
    • Boyce-Codd normal form (BCNF)

    BCNF is rarely used.


    12.1: Normal Form is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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