Final answer:
If a non-key attribute of a relation is null, the table does not automatically violate any normal form. Null values are permitted in non-key attributes across 1NF, 2NF, 3NF, and BCNF. Therefore, the correct answer is (a) NONE.
Step-by-step explanation:
When considering whether a table with a non-key attribute that is null violates any normal form, it is important to understand the definition of each normal form. In respect to the question asked:
- 1st Normal Form (1NF) requires that the table has no repeating groups and that each field contains atomic values. If a non-key attribute contains a null value, it does not violate the requirement for 1NF, as the presence of nulls is not prohibited.
- 2nd Normal Form (2NF) builds upon 1NF by adding the requirement that all non-key attributes are fully functionally dependent on the primary key. A null value does not affect this requirement either.
- 3rd Normal Form (3NF) and Boyce-Codd Normal Form (BCNF) further refine the requirements regarding dependencies, focusing on the elimination of transitive and other non-trivial dependencies. Again, the existence of a null value in a non-key attribute does not directly contravene these constraints.
Therefore, the correct answer to the question is (a) NONE. If a non-key attribute of a relation is null, that table does not automatically violate any of the normal forms listed.