Explain the concept of functional dependency in database normalization.

Functional dependency in database normalization is a constraint between two sets of attributes in a relation from a database.

In more detail, functional dependency is a fundamental concept in the theory of database normalization. It is a set of constraints between two sets of attributes in a relation. An attribute in a database is functionally dependent on another attribute if the value of the latter determines the value of the former. For instance, in a student database, the student's ID might determine the student's name, course, and grade. In this case, the name, course, and grade are functionally dependent on the student's ID.

Functional dependencies are used to define the concept of normalization in databases. Normalization is a process of organising data in a database to avoid redundancy and inconsistency. It involves decomposing a table into less redundant (and smaller) tables but without losing information. The main aim of normalization is to add, delete, and modify data without causing data anomalies.

Functional dependencies play a crucial role in achieving this goal. They help to identify the logical relationships between different attributes and to construct the right schema for the database. For example, if a functional dependency A -> B holds, it means that each value of A is associated with exactly one value of B. This can help to avoid redundancy, as we don't need to store the same information about B for each occurrence of A.

Moreover, functional dependencies are used to define keys in a database. A key is an attribute or a set of attributes that uniquely identify a record in a database. If an attribute A uniquely determines another attribute B, then A can be a key. Understanding how different data types are managed in a relational database management system can enhance comprehension of functional dependencies, as detailed in Understanding Data and Databases.

A-Level Computer Science Tutor Summary: Functional dependency in database normalization is when one set of attributes in a database relies on another set. For example, a student's ID determines their name and grades. This concept helps organise data to avoid redundancy and inconsistencies, ensuring data is accurate and easy to manage. Understanding this is key to designing efficient databases.