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Slide 10.8: Transformation rule 2 Slide 10.10: Transformation rule 3. N-N relationships Home         Print version

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Cardinality of Entity Participation

One-to-One Relationship	One-to-Many Relationship	Many-to-Many Relationship
min-card(E,R)=0   max-card(E,R)=1   min-card(F,R)=0   max-card(F,R)=1	min-card(E,R)=0   max-card(E,R)=N   min-card(F,R)=1   max-card(F,R)=1     F is the “many” side here.	min-card(E,R)=0   max-card(E,R)=N   min-card(F,R)=0   max-card(F,R)=N

The following explains the cardinality of entity participation in three relationships, teach, work, and manage:


There are different kinds of entity participation in a relationship:

• Single-valued participation if max-card(E,R)=1
• Multi-valued participation if max-card(E,R)=N
• One-to-one relationship if both E and F are single-valued
• Many-to-many relationship if both E and F are multi-valued
• Many-to-one relationship if E is single-valued and F is multi-valued, or the reverse
• Mandatory participation in R if min-card(E,R)=1. Otherwise, E is optional participation.

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Slide 10.8: Transformation rule 2 Slide 10.10: Transformation rule 3. N-N relationships Home         Print version

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My roommate says our house is haunted.           But I’ve lived here for 300 years and not noticed anything unusual.