database - 规范化为3NF，外键是否必须依赖于主键？

Question

如果每个属性都必须依赖于主键，这是否包括外键？

外键是否总是在“多”表中（在一对多关系中）？

Answer 1

3NF requires that every non-key attribute of a relation is non-transitively dependent on every candidate key. So if the foreign key you are referring to consists of a non-key attribute or attributes then the answer to your first question is yes.

A foreign key is a set of attributes subject to a referential integrity constraint. Typically that means the "many" side of a one-to-many relationship between two tables, although it's quite possible to have foreign keys in a one-to-one relationship as well.