
(b) If participation is obligatory for only one entity type, define two table types, one
for each entity. Post the identifier of the non-obligatory entity into the obligatory
entity’s table type.
(c) If participation is non-obligatory for both entity types, define three table types,
one for each entity and one for the relationship.
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Consider the assignment of patients to hospital wards. The relationship Contains
between entity types ward and Patient is 1:many (if current assignments only are
considered) since a ward may contain many patients but a patient cannot be assigned to
more than one ward. The identifiers ...