JPA 和 Postgres：查询外键答案

【问题标题】：JPA and Postgres: Querying a foreign keyJPA 和 Postgres：查询外键
【发布时间】：2018-08-14 20:32:50
【问题描述】：

我有两个实体，

评分者，与评分有一对多映射，

@Entity 
@Table(name = "Rater")
public class Rater {
    @Id
    private Long id;

    @OneToMany(mappedBy = "rater")
    private Set<Rating> ratings;

    /** constructor, getters, setters, etc. */
}

和评级，具有评级者 id 的外键

@Entity
@Table(name = "Rating")
    public class Rating {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinColumn(referencedColumnName = "id", nullable = false)
    private Rater rater;
}

我想查找 ID 为 3 的评估者所做的所有评分。我会在 Postgres 中通过如下查询来完成此操作：

SELECT rating FROM Rating rating, Rater rater WHERE rating.rater_id = rater.id AND rater.id = 3;

当我把它翻译成我的 JPA REST API 时

@RepositoryRestResource(collectionResourceRel = "rating", path = "ratings")
public interface RatingRepository extends PagingAndSortingRepository<Rating, Long> {

    @Query("SELECT rating FROM Rating rating WHERE rating.rater.id = :id")
    List<Rating> findByRaterId(@Param("id") Long id);
}

我在拨打电话时遇到错误

ERROR: column rating0_.id does not exist

如何正确查询外键？

【问题讨论】：

标签： postgresql jpa spring-boot

【解决方案1】：

改变这一行

@JoinColumn(referencedColumnName = "id", nullable = false)

到

@JoinColumn(name = "rater_id", nullable = false)

【讨论】：