Question

现在我正在计算这样的主题观点：

Long countByViewOnTopicId(Long topicId);

这相当于SQL查询

select count(*) from views where topic_id = ?

这给了我所有视图的数量，但我需要计算唯一用户的数量。我需要JPA相当于以下查询：

select count(distinct user_id) from views where topic_id = ?

我可以使用@Query注释，但我试图在项目中编写更少的自定义SQL。如下所示：

Long countDictinctUserIdByViewOnTopicId(Long topicId);

更新 `下面的条目详情：

@Entity
@Table(name = "views")
public class Views {

    @Id
    @GeneratedValue
    private Long id;

    @NotNull
    @Column(name = "user_id", insertable = false, updatable = false)
    private Long userId;

    @JoinColumn(name = "user_id")
    @ManyToOne
    private User user;

    @NotNull
    @Column(name = "topic_id", insertable = false, updatable = false)
    private Long topicId;

    @JoinColumn(name = "topic_id")
    @ManyToOne
    private Topic topic;

    @NotNull
    @Column(name = "action_type")
    @Enumerated(EnumType.ORDINAL)
    private ActionTypes actionType;

Getter, Setter...

Answer 1

尝试一下：

criteriaQuery.multiselect(criteriaBuilder.countDistinct(root));

https://en.wikibooks.org/wiki/Java_Persistence/Criteria

使用Spring JPA存储库进行不同的计数

1 个答案: