Question at position 14 Assume that a pet has 1 owner, and an owner can have more than 1 pet. What is the best way to model this relationship in the database tables above? Add the OwnerID to the Pets table as a primary keyCreate an additional junction table with Pet D and OwnerID in the table.Add PetID to the Owners table as a foreign key.Join the primary keys (PetID and OwnerID).Add OwnerID to the Pets table as a foreign key.

Question

BlackTom AI · Accepted Answer

Since each pet is owned by exactly one owner and an owner can have many pets, this is a one-to-many relationship (one Owner → many Pets). The standard relational modeling rule is: place the foreign key on the “many” side to reference the “one” side.

1) Relevant knowledge points and concepts
- Cardinality: one-to-many means many records in Pets relate to a single record in Owners.  
- Foreign key: used to enforce referential integrity by pointing from the dependent table to the primary key of the principal table.  
- Primary key uniqueness: a primary key must be unique in its table.

2) Step-by-step reasoning
- Identify sides: Owners is the “one” side (OwnerID primary key); Pets is the “many” side (PetID primary key).  
- To model one-to-many, add a column in the many-side table (Pets) that stores the Owner’s primary key.  
- Declare that column as a foreign key referencing Owners.OwnerID; PetID remains the Pets table primary key.

3) Intermediate/implementation step example
- Add column: Pets.OwnerID INT NOT NULL (if every pet must have an owner).  
- Add constraint: FOREIGN KEY (OwnerID) REFERENCES Owners(OwnerID).  
(No numerical calculation is required; these are schema steps.)

4) Why the correct answer is correct
- Putting OwnerID in Pets creates many Pets rows that can reference the same OwnerID, allowing one owner to have multiple pets while each pet has exactly one owner. Referential integrity is enforced and PetID remains the unique identifier for each pet.

5) Why the other options are incorrect (brief)
- Adding OwnerID to Pets as a primary key: incorrect because a primary key must be unique; that would prevent an owner from having multiple pets.  
- Creating a junction table: used for many-to-many relationships (not needed here).  
- Adding PetID to Owners as a foreign key: would limit each owner record to reference only one pet (wrong direction).  
- “Join the primary keys (PetID and OwnerID)”: vague and implies a composite key or unnecessary join table; not appropriate for one-to-many.

6) Conclusion
- The correct modeling is to add OwnerID to the Pets table as a foreign key. This matches the provided answer: "Add OwnerID to the Pets table as a foreign key."

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