添加子表的数量以使用休眠条件API从父表中选择

Question

如何使用Hibernate Criteria API执行此SQL查询？

SELECT c.*, count(r.id) FROM COURSE c left join REFERRAL r on c.id = r.course_id group by c.id

Answer 1

这样的事情似乎已经足够接近了：

Criteria criteria = currentSession().createCriteria(Referral.class, "r");
criteria.createAlias("r.course", "course");

ProjectionList projections = Projections.projectionList();
projections.add(Projections.groupProperty("course.id"));
projections.add(Projections.count("r.id"));

return list(criteria
        .setProjection(projections));