HQL (Hibernate Query Language) - Delete Update Example

This post shows how to perform a delete query using HQL in Hibernate application.

Hibernate Query Language (HQL) is an object-oriented query language, similar to SQL, but instead of operating on tables and columns, HQL works with persistent objects and their properties. HQL queries are translated by Hibernate into conventional SQL queries, which in turn perform an action on a database.

HQL Delete Query Syntex

The BNF for DELETE statements is the same in HQL and JPQL:

delete_statement ::=
    delete_clause [where_clause]

delete_clause ::=
    DELETE FROM entity_name [[AS] identification_variable]

HQL Delete Query Example

Example: Delete a student where id = 1;

public void deleteStudent(int id) {

        Transaction transaction = null;
        try (Session session = HibernateUtil.getSessionFactory().openSession()) {
            // start a transaction
            transaction = session.beginTransaction();

            // Delete a student object
            Student student = session.get(Student.class, id);
            if (student != null) {
                String hql = "DELETE FROM Student " + "WHERE id = :studentId";
                Query query = session.createQuery(hql);
                query.setParameter("studentId", id);
                int result = query.executeUpdate();
                System.out.println("Rows affected: " + result);
            }

            // commit transaction
            transaction.commit();
        } catch (Exception e) {
            if (transaction != null) {
                transaction.rollback();
            }
            e.printStackTrace();
        }
    }

Learn hibernate at https://www.javaguides.net/p/hibernate-tutorial.html.

Reference

https://www.javaguides.net/2018/11/hibernate-query-language-insert-update.html.