Database Normalization Tutorial with example

Normalizing a database means laying out the tables in an efficient way with the main focus being on preserving the integrity of data. If the database is normalized, there is no repetition of data.

The need for Normalization

By: sutha On 10:16 AM

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Normalization Process

• Relations can fall into one or more categories (or classes) called Normal Forms
• Normal Form: A class of relations free from a certain set of modification anomalies.
• Normal forms are given names such as:
  • First normal form (1NF)
  • Second normal form (2NF)
  • Third normal form (3NF)
  • Boyce-Codd normal form (BCNF)
  • Fourth normal form (4NF)
  • Fifth normal form (5NF)
  • Domain-Key normal form (DK/NF) 

By: sutha On 8:10 AM

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Functional Dependencies

• A Functional Dependency describes a relationship between attributes within a single relation.
• An attribute is functionally dependent on another if we can use the value of one attribute to determine the value of another.
• Example: Employee_Name is functionally dependant on Social_Security_Number because Social_Security_Number can be used to uniquely determine the value of Employee_Name.
• We use the arrow symbol -> to indicate a functional dependency.
  X -> Y is read X functionally determines Y

  Student_ID -> Student_Major
  Student_ID, CourseNumber, Semester -> Grade
  Course_Number, Section -> Professor, Classroom, NumberOfStudents
  SKU -> Compact_Disk_Title, Artist
  CarModel, Options, TaxRate -> Car_Price
      

By: sutha On 8:06 AM

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