jpa使用union

JPA并不支持直接使用UNION操作符，但可以通过使用子查询或者原生SQL来实现UNION操作。

使用子查询的方式：

CriteriaBuilder cb = entityManager.getCriteriaBuilder();
CriteriaQuery<MyEntity> query = cb.createQuery(MyEntity.class);
Root<MyEntity> root = query.from(MyEntity.class);

Subquery<MyEntity> subquery1 = query.subquery(MyEntity.class);
Root<MyEntity> subRoot1 = subquery1.from(MyEntity.class);
subquery1.select(subRoot1);
subquery1.where(cb.equal(subRoot1.get("someProperty"), someValue));

Subquery<MyEntity> subquery2 = query.subquery(MyEntity.class);
Root<MyEntity> subRoot2 = subquery2.from(MyEntity.class);
subquery2.select(subRoot2);
subquery2.where(cb.equal(subRoot2.get("someOtherProperty"), someOtherValue));

query.select(root).where(cb.or(cb.in(root).value(subquery1), cb.in(root).value(subquery2)));

使用原生SQL的方式：

Query query = entityManager.createNativeQuery(
    "SELECT * FROM my_entity WHERE some_property = :someValue " +
    "UNION " +
    "SELECT * FROM my_entity WHERE some_other_property = :someOtherValue", MyEntity.class);
query.setParameter("someValue", someValue);
query.setParameter("someOtherValue", someOtherValue);
List<MyEntity> results = query.getResultList();