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In database management systems, normalization is an essential process to ensure that data is organized efficiently and effectively. Multivalued dependency (MVD) is a concept that helps to identify and eliminate data redundancy and anomalies, and Fourth Normal Form (4NF) is a normalization form that addresses the challenges associated with multivalued dependency. In this article, we will discuss multivalued dependency, the Fourth Normal Form, and its importance in database management systems. Multivalued Dependency (MVD)Multivalued dependency (MVD) is a type of dependency that exists when a table contains more than one multivalued attribute and changes to one attribute can affect another attribute. In other words, MVD occurs when a table has a non-trivial relationship between attributes that are not part of the same composite key.
Example: Suppose there is a bike manufacturer company that produces two colors(white and black) of each model every year.
Here columns COLOR and MANUF_YEAR are dependent on BIKE_MODEL and independent of each other. In this case, these two columns can be called as multivalued dependent on BIKE_MODEL. The representation of these dependencies is shown below:
This can be read as “BIKE_MODEL multidetermined MANUF_YEAR” and “BIKE_MODEL multidetermined COLOR”. Fourth Normal Form (4NF)Fourth Normal Form (4NF) is a level of database normalization that requires a relation to be in BCNF and have no non-trivial multivalued dependencies other than the candidate key, to eliminate redundant data and maintain data consistency. If a table violates this standard, it needs to be split into two tables to achieve 4NF. For a relation R to be in 4NF, it must meet two conditions −
Example: To remove the multivalued dependency (MVD) in the “Students” table example, we can create two new tables, one for “Courses” and another for “Textbooks,” and establish a relationship between them using foreign keys. Here’s how we can create the tables: Table 1: Students
Table 2: Courses
Table 3: Textbooks
So, we removed the multivalued dependency by splitting the “Course” and “Textbook” columns into separate tables. We have also added a new “Course ID” column to the “Students” table. It has a foreign key that references the “Course ID” column in the “Courses” table. Similarly, the “Textbooks” table also has a “Course ID” column that serves as a foreign key referencing the “Course ID” column in the “Courses” table. Hence, we have achieved the fourth normal form (4NF) for the “Students” table. It has done after by removing the multivalued dependency and creating separate tables. The Resultant schema eliminates data redundancy and improves data integrity, making it easier to manage and query the database. Challenges of Fourth Normal FormAchieving 4NF can be challenging, as it requires careful analysis of functional dependencies, selecting appropriate keys, and balancing between normalization and performance. Achieving 4NF can be time-consuming, and it may require additional storage space. Examples of Achieving Fourth Normal FormAn example of achieving 4NF is splitting a table with MVDs into two or more tables, with each table containing attributes that are functionally dependent on the primary key. In another example, an intersection table can be used to eliminate MVDs by creating a separate table that links two other tables with MVDs. Example: MOVIE
The table is not in it 4th Normal Form, as the various locations can have the same movie, and multiple movies can have same listing. Therefore, let’s split the table to achieve 4th Normal Form. LOCATION
GENRE
Now, the table has achieved its 4th Normal Form, by splitting the tables and converting it into its violation free table. ConclusionMultivalued dependency is a concept which can be removed by 4NF. 4NF helps to eliminate data redundancy, improve data integrity, and improve database performance. Achieving 4NF can be challenging. But it improves data quality, better database performance, and less anomalies associated that has data redundancy. By analyzing functional dependencies and using appropriate techniques, 4NF can be achieved. Frequently Asked Quesions on Multivalued Dependency and Fourth Normal Form – FAQsWhat are the benefits of achieving 4NF?
How does MVD differ from other types of dependencies?
What are some common techniques for achieving 4NF?
When should I consider applying 4NF to my database design?
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Reffered: https://www.geeksforgeeks.org
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Type: | Geek |
Category: | Coding |
Sub Category: | Tutorial |
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