Question

我的JPA实体类如下：

@Entity
@Table(name = "users")
public class User implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    private Long id;

...

    // bi-directional many-to-many association to Tag
    @ManyToMany
    @JoinTable(name = "user_tags_preferences", joinColumns = { 
            @JoinColumn(name = "user_id") }, 
    inverseJoinColumns = {
            @JoinColumn(name = "tag_id") })
    private List<Tag> tags;

@Entity
@Table(name = "tags")
public class Tag implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    private Long id;

    private String name;

...

    // bi-directional many-to-many association to CookEvent
    @ManyToMany(mappedBy = "tags")
    private List<CookEvent> cookEvents;

    // bi-directional many-to-many association to User
    @ManyToMany(mappedBy = "tags")
    private List<User> users;

@Entity
@Table(name = "cook_events")
public class CookEvent implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    private Long id;

    @Column(name = "takes_place_on")
    private LocalDateTime takesPlaceOn;

...

    // bi-directional many-to-many association to Tag
    @ManyToMany
    @JoinTable(name = "cook_events_tags", joinColumns = { 
            @JoinColumn(name = "cook_event_id") }, 
    inverseJoinColumns = {
            @JoinColumn(name = "tag_id") })
    @OrderBy("name")
    private List<Tag> tags;

因此，在数据库中，我具有“用户”，“ cook_events”，“标签”，“ user_tags_preferences”，“ cook_events_tags”表。我将需要执行以下操作的JPQL查询：

在我的前端，我有user_id。我想要一个查询，用于过滤所有takesPlaceOn > CURRENT_TIMESTAMP的cook_event，以及我的user_id中至少有一个user_tags_preferences与cook_event_tags匹配的查询。

联接是否有可能过滤所有这些，最终最终得到我需要的List<CookEvent>。甚至更容易使用List<Tag>。

它甚至可以是不同的查询，我自己在后端对其进行过滤，但我想尝试过滤查询中的所有内容。

Answer 1

这仅仅是答案吗？

SELECT DISTINCT(c) from User u JOIN u.tags t JOIN t.cookEvents c
WHERE u.id = :id AND c.takesPlaceOn > CURRENT_TIMESTAMP

Answer 2

步骤1。将所有多对多关联中的列表替换为 Set 。

第2步。将JPQL查询更改为：从CookEvent中选择SELECT c参加FETCH c.tags t参加FETCH t.users u在哪里c.takesPlaceOn> CURRENT_TIMESTAMP和u.id =：id

谁可以进行此JPQL查询？

2 个答案: