One To One Query in JPA springboot In JPA and Spring Boot, you can perform a one-to-one query using JPQL (Java Persistence Query Language) or by using Spring Data JPA's query methods. Assuming you have two entities, let's call them EntityA and EntityB, with a one-to-one relationship between them, you can write a JPQL query to retrieve EntityA and its associated EntityB as follows: @Entity public class EntityA { @Id private Long id; @OneToOne(mappedBy = "entityA") private EntityB entityB; // ... } @Entity public class EntityB { @Id private Long id; @OneToOne @JoinColumn(name = "entity_a_id") private EntityA entityA; // ... } ------------------------------------------------------------------------------ TypedQuery<EntityA> query = entityManager.createQuery( "SELECT a FROM EntityA a JOIN FETCH a.entityB b WHERE a.id = :id", EntityA.class); query.setParameter("id", entityId); EntityA e...