@JoinTable的JPA查询

Question

场景：I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 (中间表)不是一个实体，所以无法得到结果。有人能建议一个JPQ来连接连接表吗？

Answer 1

您可以使用实体对象加入，没有必要使用“ON”。举个例子，

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