Spring JPA CriteriaQuery分组查询

Question

Spring JPA CriteriaQuery 设置select 查询的字段丝毫没起到作用，很郁闷、网上也有很多类似的问题，都没有解决方法。有没有大神用JPA做过分组查询的？求教。。。

Answer 1

CriteriaQuery q = cb.createQuery(Country.class);
Root c = q.from(Country.class);
q.select(c.get("currency"), cb.sum(c.get("population")));
q.where(cb.isMember("Europe", c.get("continents")));
q.groupBy(c.get("currency"));
g.having(cb.gt(cb.count(c), 1));

对应的sql 语句
SELECT c.currency, SUM(c.population)

FROM Country c
WHERE 'Europe' MEMBER OF c.continents
GROUP BY c.currency
HAVING COUNT(c) > 1

api地址：http://www.objectdb.com/java/jpa/query/jpql/group#GROUP_BY_and_HAVING_in_Criteria_Queries_