问题:

I need to bring from DB only one single result. How can I do that with JPA?

Select top 1 * from table

I tried

"select t from table t"

query.setMaxResults(1);

query.getSingleResult();

but didn't work. Any other ideas?

回答1:

Try like this

String sql = "SELECT t FROM table t";
Query query = em.createQuery(sql);
query.setFirstResult(firstPosition);
query.setMaxResults(numberOfRecords);
List result = query.getResultList();

It should work

UPDATE*

You can also try like this

query.setMaxResults(1).getResultList();

回答2:

To use getSingleResult on a TypedQuery you can use

query.setFirstResult(0);
query.setMaxResults(1);
result = query.getSingleResult();

回答3:

The easiest way is by using @Query with NativeQuery option like below:

@Query(value="SELECT 1 * FROM table ORDER BY anyField DESC LIMIT 1", nativeQuery = true)

回答4:

Use a native SQL query by specifying a @NamedNativeQuery annotation on the entity class, or by using the EntityManager.createNativeQuery method. You will need to specify the type of the ResultSet using an appropriate class, or use a ResultSet mapping.