使用Hibernate Criteria从日期中选择不同的年份

Question

I would like to get all distinct years from a MySQL date field with the Hibernate Criteria API. This is the query that I want to translate to criteria:

sess.createQuery("SELECT DISTINCT year(o.date) FROM Observation");

I've tried :

Criteria crit = sess.createCriteria(Observation.class)
    .setProjection(Projections.distinct(Projections.property("year(date)")));

But it returns an error

ERROR - could not resolve property: year(date) of: ca.ogsl.biodiversity.hibernate.Observation

Does any body knows if it's possible and how?

Thanks a lot!!!

Keven

Answer 1

尝试使用sql投影，因此您可以使用任何SQL表达式：

criteria.setProjection(Projections.sqlProjection( "yeard(DATE_COLUMN_NAME) as year", new String[] {"year"}, new Type[] {StandardBasicTypes.INTEGER} ));  

Answer 2

使用DISTINCT关键字查询不同年份，而不是查看所有年份并尝试在Java代码中过滤它们。

SELECT DISTINCT year(o.date) FROM Observation;