BCS 260 Lecture Notes - Lecture 4: Foreign Key
Document Summary
The relationship between a strong and weak entity is termed an identifying relationship if the weak entity is id-dependent: represented by a solid line. The relationship between a strong and weak entity is termed a nonidentifying relationship if the weak entity is non-iddependent: represented by a dashed line, also used between strong entities. Understand nonidentifying and identifying relationships and how to use them. All id-dependent entities are weak entities, but there are other entities that are weak but not id-dependent. All id-dependent entities are weak entities, but there are other entities that are weak but not iddependent. A non-id-dependent weak entity may have a single or composite identifier, but the identifier of the parent entity will be a foreign key. Vehicle is an auto_model and if that particular. Auto_model did not exist, the vehicle itself would never have existed, this is why weak, but non-id dependent.
