What is a transitive dependency, and in which normal form is it removed?

• A. A transitive dependency occurs when non-key attributes depend on other non-key attributes; 3NF removes it.
• B. A transitive dependency occurs when a non-key attribute depends on the primary key; 2NF removes it.
• C. It occurs when a key depends on a non-key attribute; BCNF removes it.
• D. It occurs when a derived attribute depends on a key; 1NF removes it.

Answer: (A)

Transitive dependency is about a chain of dependencies where a key determines a non-key attribute, which in turn determines another non-key attribute. In practical terms, you have something like A (a key) → B (a non-key) and B → C (another non-key). Because C depends on A only through B, C is transitively dependent on the key. Normalizing to third normal form removes this situation by ensuring non-key attributes depend only on candidate keys, not on other non-key attributes. That’s why the statement that a transitive dependency occurs when non-key attributes depend on other non-key attributes, and that 3NF removes it, is best. The other descriptions misstate what drives the dependency and which normal form addresses it: for example, saying a non-key attribute depends on the primary key describes a direct (not transitive) dependency and is not what 2NF targets; BCNF deals with determinants being superkeys, not a non-key depending on a key; and 1NF is about atomic values, not transitive dependencies.