ER Modelling

Question

Which of the following statements are true about weak entity sets

1. a weak entity set cannot have a primary key

2. a weak entity set must have a local attribute in primary key

3.a weak entity must borrow an attribute from another entity set to form a primary key

(a) 1 and 2

(b) 2 and 3

(c) 3 only

(d) None

Answer 1

B is answer

1. weak entity can have primary key by combining weak entity with weak relation. so false

2.a weak entity set must have a local attribute in primary key.  true but  since it borrow attribute from attribute from strong entity  to make primary key. so we can say all local attribute must not present.

3.a weak entity must borrow an attribute from another entity set to form a primary key . Is true only

Comments

what is identifying owner the new primary key for weak entity set  or the primary key of another entity which is used to combine with local attributes.....

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identifying or owner is Strong entity set. 

Owner the new primary keyof Strong entity which is used to combine with local attributes of weak entity.

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I think 1st statement is true because A weak entity set in itself cannot have a primary key.That's why we combine it with key of strong entity set.

Answer 2

b is the answer of this question.