Identifiers weak entities what surrogate primary key

weak entity can only exist when owned by another one. Example a Room can

stores each degree in a separate record(it will use the 1:M relationship between

What is a composite entity, and when is it used? Used to transform M:N

relationships to 1:M relationships. When PK attributes are inherited from entities that relate to one another.

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		a weak relationship Dashed line
7.	
7.

9.	What is a derived attribute? Give an example. A value calculated from other

attributes. The total cost of an order is found from multiplying quantity ordered by unit price.

combines the multiple entities and relationship which relate each other into a

	Under what circumstances are composite primary keys appropriate?

once in M:N relationship. Identifiers of weak entities