Oracle Database SQL — Question 150

Which two statements are true about Entity Relationships? (Choose two.)

Answer options

• A. A one-to-one relationship is always a self-referencing relationship.
• B. A relationship can be mandatory for both entities.
• C. A many-to-many relationship can be implemented only by using foreign keys.
• D. A one-to-many relationship in one direction is a one-to-one relationship in the other direction.
• E. A table name can be specified just once when selecting data from a table having a self-referencing relationship.

Correct answer: B, D

Explanation

Option B is correct because relationships can indeed be mandatory for both entities, ensuring that each entity must have a corresponding relationship. Option D is also accurate, as a one-to-many relationship from one entity can imply a one-to-one relationship when viewed from the other entity's perspective. The other options are incorrect as they misrepresent the characteristics of relationships.