What Is Fourth Normal Form (4NF)?

Fourth Normal Form, also known as 4NF, is a notion of database design that helps guarantee that a database is arranged in a way that reduces repetition and is dependent on other parts of the database. Put another way, it helps maintain the orderliness of your database and prevents problems such as data discrepancies and update anomalies. Before attempting to comprehend 4NF, a fundamental familiarity with the idea of normalized is required. The process of normalize involves partitioning a huge and complicated database into several smaller tables that are better ordered. This reduces repetition and dependency, making updates and queries easier. There are multiple normal forms, with each one expanding on the principles established by the one that came before it. In the first normal form, often known as 1NF, the emphasis is placed on arranging the data in tables and determining a primary key for each table individually. In 2NF, all non-key properties are totally dependent on the primary key. The third normal form, or 3NF, removes transitive dependencies. Moving on to 4NF now. 4NF adds a constraint that a table cannot have numerous multi-valued independent dependencies. Confused? Allow us to illustrate with a concrete example. Imagine that you have access to a database that contains all of the employees at a corporation. Each employee has a unique ID, name, address, and phone number in a table. Each department has a unique ID and name in a table. Within the parameters of this scenario, it is possible for a person to hold positions in more than one department, and it is also possible for a department to have more than one employee. This establishes a relationship between the two tables known as a many-to-many relationship. You might create a third table that you'd call the "employee department" to represent this relationship. This table would have a foreign key that would connect it to both the employee table and the department table. Having said that, this configuration results in a multi-valued dependency. The "department" characteristic of an employee is reliant not only on the individual's ID but also on the Reference number of the department to which the employee belongs. This is against the 4NF principle because it results in several independent dependencies. In order to rectify this situation, you will need to generate a distinct table for each multi-valued dependent. Therefore, in this scenario, you would need to build a database for "employee department1" as well as a list for "employee department2," both of which would have a foreign key for the employee and department tables. This guarantees that there is only a single independent multi-valued dependency, one per table, which satisfies the prerequisites of the 4NF standard.