mysql - JPA- hibernate : How to select the key/value of a map attribute using KEY/VALUE syntax with JPQL

Question

我有以下具有相应 getter/setter 的实体:

@Entity
public class Movie {
   @Id@GeneratedValue 
   private int id;
       private String title;   
//getters and setters
}

@Entity
public class VideoStore {

  @Id@GeneratedValue
  private int id;
  private String name;

  @ElementCollection
  @CollectionTable(name="INVENTORY",joinColumns=@JoinColumn(name="STORE_ID"))
  @Column(name="COPIES_IN_STOCK")
  @MapKeyJoinColumn(name="MOVIE",referencedColumnName="ID")
  Map<Movie,Integer>videoInventory;
//getters and setters
}

我尝试从主方法执行以下 JPQL 查询:

    EntityManagerFactory emf=Persistence.createEntityManagerFactory("Tutorial");
    EntityManager em=emf.createEntityManager();
    String queryMap1 = "SELECT v " +
            "FROM VideoStore v JOIN v.videoInventory m " +
            "WHERE KEY(m) = 1";
    @SuppressWarnings("rawtypes")
    List results= em.createQuery(queryMap1).getResultList();

我收到以下错误:

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'KEY(videoinven1_.COPIES_IN_STOCK)=1' at line 1

此外，包含 KEY/VALUE/ENTRY 语法的查询的每个变体都会出现不同类型的错误

我使用 JPA 与 Hibernate 和 Mysql 作为数据库提供程序。我找不到此问题的答案，因此非常感谢您的帮助。

Answer 1

您似乎将 KEY(m)(这是一个 Movie)的返回值与数字进行比较。