Question: What is a functional dependency in the context of relational databases?

Options:

1. A relationship between two tables
2. A constraint that describes the relationship between attributes
3. A method of indexing data
4. A type of normalization

Correct Answer: A constraint that describes the relationship between attributes

Solution:

A functional dependency describes a constraint between two attributes in a relation, indicating that the value of one attribute is determined by the value of another.