Question

我在我的项目中使用了hibernate，并且我试图将现有的sql查询从DaoImplementation类转换为hql，

我的SQL查询是

JdbcTemplate select = new JdbcTemplate(dataSource);
    String sql = "SELECT * FROM (SELECT site_id,rtc,sigplan,cycle_time,health,phase_no,phase_time,active_groups,groupscolour,ip "+
                 "FROM status_data where  rtc>='" + fromDate + "' and rtc<'" + toDate + "' and "+
                 "site_id=" + SiteId + " order by rtc desc limit "+recordLimit+" )as temp ORDER BY RTC ASC";

我写了hql版本以从HealthLog表中获取数据

String hql = " select f from (select h from HealthLog h where rtc>='"+fromDate+"' and rtc <'"+toDate+"' "
            + "and siteId = "+siteId+" order by rtc desc limit "+limit+" ) as f order by rtc asc ";
    return super.readListByHql(hql);

但是上面的hql引发了以下异常

org.hibernate.hql.internal.ast.QuerySyntaxException: unexpected token: ( near line 1, column 16 [ select f from (select h from com.traff.hibernate.model.HealthLog as h where rtc>='1974-08-01 14:10:00.0' and rtc <'1974-09-01 23:46:20.6' and siteId = 20 order by rtc desc limit 50000 ) as f order by rtc asc ]
at org.hibernate.hql.internal.ast.QuerySyntaxException.convert(QuerySyntaxException.java:54)
at org.hibernate.hql.internal.ast.QuerySyntaxException.convert(QuerySyntaxException.java:47)
at org.hibernate.hql.internal.ast.ErrorCounter.throwQueryException(ErrorCounter.java:79)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.parse(QueryTranslatorImpl.java:276)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:180)
at org.hibernate.hql.intern

我还尝试了下面的代码片段，但这给了我错误的结果

Criteria criteria = createEntityCriteria();     
    criteria.add(Restrictions.ge("rtc", fromDate));
    criteria.add(Restrictions.lt("rtc", toDate));
    criteria.add(Restrictions.eq("siteId", siteId));
    criteria.setMaxResults(limit);
    criteria.addOrder(Order.asc("rtc"));            
    criteria2 = criteria;
    criteria2.addOrder(Order.desc("rtc"));      
    return criteria2.list();

实现结果的正确方法是什么？

Answer 1

首先，正如评论中已经提到的，您不能在HQL中的FROM子句中执行子查询。请参阅：Hibernate Documentation

其次，HQL不支持limit关键字。通常，您将使用query.setFirstResult(0)和query.setMaxResults(recordLimit)方法，其中查询具有查询接口的类型。但是因为你在子查询中使用限制，所以没有办法。请参阅：How to set a limit to inner query in Hibernate?

一些选项：

使用本机SQLQuery
由于您只在外部查询中进行排序。您只能执行内部查询并使用Java进行排序。

选项2的示例：

Session session = factory.openSession();
Query query = session
    .createQuery("FROM HealthLog "
        + "WHERE rtc >= :rtcL and rtc < :rtcG and siteId = :siteId "
        + "ORDER BY rtc DESC");
query.setParameter("rtcL", fromDate);
query.setParameter("rtcG", toDate);
query.setParameter("siteId", siteId);
query.setFirstResult(0);
query.setMaxResults(recordLimit);
List<HealthLog> res = query.list();
session.close();

Collections.sort(res, new Comparator<HealthLog>() {
  public int compare(HealthLog o1, HealthLog o2) {
    return o1.getRtc().compareTo(o2.getRtc());
  }
});

上面的查询返回具有所有属性的HealthLogs。如果您只想检索特定属性，可以使用SELECT new HealthLog(siteId,rtc,sigplan,cycle_time,...)中的拟合构造函数向查询中添加HealthLog。

请注意，代码段可能无法使用，因为我不知道您的型号和属性名称。

sql到hql抛出异常

1 个答案: