摘要：
Understanding Relationship Existence Existence describes the relationship between a pair of entities from the perspective of the child entity. Fundamentally, it asks the question, "Is a foreign key... 阅读全文
摘要：
Understanding Relationship Cardinality Cardinality describes the quantitative dimension in the relationship between a pair of entities as viewed from the perspective of the parent entity. Fundament... 阅读全文
摘要：
Understanding Relationship Types DEF1X supports three relationship types: Identifying Non-Identifying Non-Specific The selection of relationship types is fundamental to the referential integri... 阅读全文