引用条件查询中的早期别名字段

Question

在此查询中:

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Tuple> q = cb.createTupleQuery();

// FROM GamePlayedEvent gpe
Root<GamePlayedEvent> gpe = q.from(GamePlayedEvent.class);
// SELECT gameId, COUNT(*) AS count, AVG(duration)
// AS avDur, AVG(rewardCurrency) AS avCur, AVG(rewardXP) avXp
q.select(cb.tuple(
    gpe.<String>get("gameId"),
    cb.count(gpe).alias("count"),
    cb.avg(gpe.<Double>get("duration")).alias("avDur"),
    cb.avg(gpe.<Integer>get("rewardCurrency")).alias("avCur"),
    cb.avg(gpe.<Integer>get("rewardXp")).alias("avXp")
));
// WHERE loginTime BETWEEN ...
q.where(cb.between(gpe.<Date>get("time"), fromTime, toTime));
// GROUP BY gameId
q.groupBy(gpe.<String>get("gameId"));
// ORDER BY count DESC
q.orderBy(cb.desc(???));

如何添加ORDER BY count DESC,引用SELECT条款中定义的"计数" ？

Answer 1

如果你刚刚捕获了count表达式并直接使用它会怎么样？

Expression event_count = cb.count(gpe);

q.select(cb.tuple( 
  gpe.<String>get("gameId"), 
  event_count,
  ... 
)); 

q.orderBy(cb.desc(event_count));