JPA: JOIN in JPQL

by

Join on one-to-many relation in JPQL looks as follows:

select b.fname, b.lname from Users b JOIN b.groups c where c.groupName = :groupName

When several properties are specified in select clause, result is returned as Object[]:

Object[] temp = (Object[]) em.createNamedQuery("...")
    .setParameter("groupName", groupName)
    .getSingleResult(); 
String fname = (String) temp[0];
String lname = (String) temp[1];

By the way, why your entities are named in plural form, it’s confusing. If you want to have table names in plural, you may use @Table to specify the table name for the entity explicitly, so it doesn’t interfere with reserved words:

@Entity @Table(name = "Users")     
public class User implements Serializable { ... }

More Related Contents:

  1. Parameter in like clause JPQL
  2. The JPA hashCode() / equals() dilemma
  3. JPQL Create new Object In Select Statement – avoid or embrace?
  4. Adding IN clause List to a JPA Query
  5. Please explain about insertable=false and updatable=false in reference to the JPA @Column annotation
  6. How to use multiple JOIN FETCH in one JPQL query
  7. Limit number of results in JPQL
  8. stream on JPA lazy list
  9. How To Define a JPA Repository Query with a Join
  10. Using the JPA Criteria API, can you do a fetch join that results in only one join?
  11. Doing an “IN” query with Hibernate
  12. Setting a parameter as a list for an IN expression
  13. JPQL: Receiving a Collection in a Constructor Expression
  14. How can I avoid the Warning “firstResult/maxResults specified with collection fetch; applying in memory!” when using Hibernate?
  15. Java8 Collections.sort (sometimes) does not sort JPA returned lists
  16. IN-clause in HQL or Java Persistence Query Language
  17. Disable caching in JPA (eclipselink)
  18. JPA Native Query select and cast object
  19. Spring Data JPA and Exists query
  20. JPQL Like Case Insensitive
  21. No operator matches the given name and argument type(s). You might need to add explicit type casts. — Netbeans, Postgresql 8.4 and Glassfish
  22. Is it possible to write a generic enum converter for JPA?
  23. How to create a JPA query with LEFT OUTER JOIN
  24. Why does this stream return no element?
  25. What’s the difference between the IN and MEMBER OF JPQL operators?
  26. EclipseLink 2.7.0 and JPA API 2.2.0 – signature mismatch
  27. What is a JPA implementation?
  28. JPA Select latest instance for each item
  29. How to use Postgres JSONB datatype with JPA?
  30. JPA: Implementing Model Hierarchy – @MappedSuperclass vs. @Inheritance

Leave a Comment