JPA-从数据库表中检索数据wrt外键-

Question

I am trying to retrieve data from a table which has a foreign key, "reg_no". And the foreign key is not unique, it can be duplicated.

Now I want to retrieve the data from this table using this foreign key. I will provide a "reg_no" and the Java Persistence API will retrieve a list of the result set from the table wrt to "reg_no" provided.

Please enlighten me how can I solve this problem?

Answer 1

You can do something like this, using JPQL:

String queryString = "SELECT t FROM YourTable t " +
                     "WHERE reg_no = :regNo";
Query query = getEntityManager().createQuery(queryString); 
query.setParameter("regNo", regNoValue);
return query.getResultList();

Answer 2

EntityManager entityManager = entityManagerFactory.createEntityManager();
List results = em.createQuery("SELECT c FROM Vehicle v WHERE reg_no = :reg_no").setParameter("reg_no", new String("0000")).getResultList;