Learning Objectives
- ERD的零件
- relationship的defined, refined, 和資料庫設計的過程
- ERD components affect database design and implementation
- That real-world database design often requires the reconciliation of conflicting goals
ERM

Attributes

粗體為Required,Chen Model無法表示

Identifiers可包含多個attribute

Composite attribute:可拆分成多個attribute的attribute,如地址拆成縣市、街道等等。
Multivalued attributes:一個人有好幾個學位。

若當作candidate key組合(composite identifier)不能重複,單獨attribute可以
Multiple Attribute

粗體為PK
