我正在为下表寻找适当的 JPQL 查询，以便它可以在 java 代码中工作，它不应该是本机查询

Question

以下是我无法进行正确 JPQL 查询的表架构

  Mobile table     | hardware table       |  releases table
  --------------------------------------------------------------
  id pk            |   id  pk            | id  pk
  name varchar         size  varchar       launchdate varchar
  hardware_id fk   |   pdname varchar    | tally  varchar
  releases_id fk   |                     | 

 i have tried all below query's in my code but it all gives error for:
  //String qry="Select m.name,h.size,h.pdname from com.example.users.Mobile m, 
   com.example.users.entities.Hardware h where m.hardware_id=h.id ";


    //String qry="Select m from Mobile m inner join fetch m.hardware h where m.hardware_id=h.id";

    //String qry = "SELECT m FROM Mobile m JOIN m.hardware_id h WHERE m.hardware_id = h.id";

    String qry="select m.name from mobile m,hardware h where m.hardware_id=h.id";


   System.out.println("in entity manager Query is "+ qry);

    Query query = entityManager.createQuery(qry);

    return query.getResultList();

错误：org.hibernate.hql.internal.ast.QuerySyntaxException：移动设备未映射

 This is what i have in Mobile Entity

  @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name ="hardware_id",referencedColumnName = "id")
 private Hardware hardware;

 @OneToOne(cascade = CascadeType.ALL)
 @JoinColumn(name="releases_id",referencedColumnName = "id")
 private Releases releases;

Answer 1

您在@JoinColumn 中指定的名称是数据库列而不是您的实体属性名称。 问题是您将属性名和列名混合在一起。

查询：

"SELECT m FROM Mobile m JOIN Hardware h ON m.hardware.id = h.id"

Answer 2

Mobile 实体中是否有这样的属性？

    @ManyToOne(optional = false)
    @JoinColumn(name = "hardware_id")
    private Hardware hardware;