Lecture 3 — ER Model & ER Diagram

Entities & attributes, keys, relationship sets, degree, mapping cardinality, participation, weak entities, ER-diagram notation, and EER concepts.

Sections

🔑

Entities, Attributes & Keys

Entity vs entity set, all attribute types, domains, and the key hierarchy.

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Relationships & Cardinality

Relationship sets, degree, mapping cardinality, participation, weak entities & roles.

🔷

ER Diagram & EER

Full notation summary, a worked university ER diagram, and specialization/aggregation.

Quick summary

ER MODEL = 3 concepts: Entity sets · Relationship sets · Attributes.

ATTRIBUTE TYPES: Simple/atomic · Composite · Single-valued · Multi-valued
   (double oval) · Derived (dashed oval) · Key (underline).

KEYS: Super ⊇ Candidate (minimal) ⊇ Primary. Foreign = PK borrowed from another set.

RELATIONSHIPS: degree (binary/ternary) · mapping cardinality 1:1, 1:N, N:1, N:N.
PARTICIPATION: total (double line, must) vs partial (single line, may).
WEAK ENTITY: double rectangle · double diamond · dashed-underline discriminator;
   PK = owner PK + discriminator.

NOTATION: rectangle=entity · diamond=relationship · oval=attribute · underline=key.
EER: specialization/generalization (ISA triangle) · aggregation.