Which one of the following is used to represent the supporting many-one…
2020
Which one of the following is used to represent the supporting many-one relationships of a weak entity set in an entity-relationship diagram ?
- A.
Diamonds with double/bold border
- B.
Rectangles with double/bold border
- C.
Ovals with double/bold border
- D.
Ovals that contain underlined identifiers
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Correct answer: A
Answer: Diamonds with double/bold border (identifying relationship).
Explanation:
The supporting relationship between a weak entity and its owner is called an identifying relationship and is depicted as a diamond with a double (bold) border.
A weak entity set itself is drawn as a rectangle with a double border; that is different from the double-lined diamond used for the identifying relationship.
Attributes are shown as ovals; a double-lined oval usually denotes a multivalued attribute, not a relationship.
Weak entities often have a partial key (discriminator), commonly indicated with a dashed underline on the partial key attribute.
In many-one identifying relationships, each weak entity instance is associated with exactly one owner instance, while an owner may be associated with many weak entity instances.