@JoinTable 的 JPA 查询

Question

场景： 我有两个实体用户和程序

@Entity
@Table(name = "user")
public class UserEntity implements Serializable{

   @Id
   public Long id;

   public String firstName;

   public String email;

   @OneToOne(cascade = CascadeType.ALL)
   @JoinTable(
      name = "user_program",
      joinColumns = {
         @JoinColumn(name = "user_id", referencedColumnName = "id")  
      },
      inverseJoinColumns = {
         @JoinColumn(name = "program_id", referencedColumnName = "id")
      }
   )
   public ProgramEntity program;
}

JPQL:

SELECT
   Program.name,
   COUNT(user.id) AS user_count
FROM UserEntity AS user
INNER JOIN ProgramEntity AS program on ________ GROUP BY Program.name

我试图获取每个程序中的用户数，但由于 JoinTable（中间 table）不是实体，所以无法获取结果。任何人都可以建议一个 JPQ 来连接连接 table?

Answer 1

您可以使用实体对象加入，'ON'不是必需的。例如，

SELECT prg.name, COUNT(user.id) AS user_count FROM UserEntity AS user INNER JOIN user.program AS prg GROUP BY prg.name

@JoinTable 的 JPA 查询

JPA Query for @JoinTable

java

hibernate

jpa

jpql

spring-boot