@OneToOne relationship in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the @OneToOne annotation represent in Spring Boot?

It represents a one-to-one relationship between two entities, meaning each instance of one entity is linked to exactly one instance of another entity.

intermediate

How do you specify the owning side in a @OneToOne relationship?

The owning side is the entity that contains the foreign key and uses the @JoinColumn annotation to specify the column that joins the two tables.

intermediate

What is the purpose of the mappedBy attribute in a @OneToOne relationship?

It is used on the inverse side to indicate that the relationship is controlled by the other entity's field, avoiding duplicate foreign keys.

advanced

Can a @OneToOne relationship be lazy loaded in Spring Boot?

Yes, by default @OneToOne is eager, but you can set fetch=FetchType.LAZY to load the related entity only when accessed.

beginner

What happens if you don't specify @JoinColumn in a @OneToOne relationship?

Spring Boot will create a default foreign key column with a generated name, which might not match your database schema or naming conventions.

In a @OneToOne relationship, which side owns the foreign key?

A The side with the @JoinColumn annotation

B The side with the mappedBy attribute

C Both sides share the foreign key equally

D Neither side owns the foreign key

The owning side is the entity with the @JoinColumn annotation that holds the foreign key.

What does the mappedBy attribute do in a @OneToOne relationship?

A Removes the relationship

B Defines the owning side of the relationship

C Creates a new foreign key column

D Specifies the inverse side and points to the owning side's field

mappedBy tells Spring Boot which field owns the relationship to avoid duplicate foreign keys.

How do you make a @OneToOne relationship load lazily?

A Lazy loading is not possible with @OneToOne

B Use @Lazy annotation on the entity class

C Set fetch=FetchType.LAZY on the @OneToOne annotation

D Set fetch=FetchType.EAGER

Setting fetch=FetchType.LAZY delays loading the related entity until it is accessed.

What is the default fetch type for @OneToOne in Spring Boot?

A EAGER

B NONE

C LAZY

D MANUAL

By default, @OneToOne relationships are eagerly fetched.

If you omit @JoinColumn in a @OneToOne relationship, what happens?

A An error occurs at runtime

B Spring Boot creates a default foreign key column

C The relationship is ignored

D The database schema is not updated

Spring Boot generates a default foreign key column name if @JoinColumn is not specified.

Explain how to set up a @OneToOne relationship between two entities in Spring Boot, including owning and inverse sides.

Think about which entity holds the foreign key and how to avoid duplicate keys.

Describe the difference between the owning side and the inverse side in a @OneToOne relationship.

Consider who 'owns' the link in the database.