Non-key Attributes Non-key attributes can be in only one entity. Unlike key attributes, non-key attributes never migrate from parent to child entities. Assign the attributes to the associated entities begins by the modeler and validate the assignment by normalization. Rules: In general, entities with the same primary key should be combined into one entity. Place non-key attributes in the parent entity for parent-child relationships as long as it makes sense. If a parent entity has no non-key attributes, combine the parent and child entities.