CREATE TABLE testTable (
  col1 NUMBER(38, 0)
);

INSERT INTO testTable VALUES (012345678901234567890123456789);
COMMIT;

@PersistenceContext(unitName = ...)
private EntityManager em;
    
Query query = em.createNativeQuery("SELECT col1 FROM testTable);
Object queryResult = query.getSingleResult(); // Will be of type BigDecimal as expected

@PersistenceContext(unitName = ...)
private EntityManager em;
    
Query query = em.createNativeQuery("SELECT col1 FROM testTable UNION ALL SELECT 43.543 AS col1 FROM DUAL);
List<Object> queryResults = query.getResultList(); // Will be of type Float. This is kind of unexpected

@PersistenceContext(unitName = ...)
private EntityManager em;
    
Query query = em.createNativeQuery("SELECT 012345678901234567890123456789 AS col1 FROM DUAL);
Object queryResult = query.getSingleResult(); // Will be of type Float. This is kind of unexpected