Hibernate - (HQL and JPQL) Select statements

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SELECT statements in HQL is:

select_statement :: =
    [select_clause]
    from_clause
    [where_clause]
    [groupby_clause]
    [having_clause]
    [orderby_clause]

The simplest possible HQL SELECT statement is of the form:


List<Person> persons = session.createQuery("from Person" ).list();

The select statement in JPQL is exactly the same as for HQL except that JPQL requires a select_clause, whereas HQL does not.

List<Person> persons = entityManager.createQuery(
"select p " +
"from Person p", Person.class )
.getResultList();

Even though HQL does not require the presence of a select_clause, it is generally good practice to include one. For simple queries the intent is clear and so the intended result of the select_clause is easy to infer. But on more complex queries that is not always the case.

It is usually better to explicitly specify intent. Hibernate does not actually enforce that a select_clause be present even when parsing JPQL queries, however, applications interested in JPA portability should take heed of this.

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