JPA Query for @JoinTable

Question

Scenario: I have two entities User and Program

@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

I tried to get the number of users in each program but I couldn't get the result due to the JoinTable (intermediate table) is not an entity. Can anyone suggest a JPQ to connect the join table?

Answer 1

You can join using the entity object, 'ON' is not necessary. For you example,

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