遍历节点不能为空（Hibernate SQL） [英] node to traverse cannot be null (Hibernate SQL)

问题描述

我通过hibernate执行SQL查询，如下所示：

  SELECT thi 
 FROM track_history_items thi 
 JOIN artists art 
 ON thi.artist_id = art.id 
 WHERE thi.type =TrackBroadcast
 GROUP BY art.name 
 ORDER thi.createdAt DESC 
  

但我收到'Node遍历的消息不能为null！'的消息。任何人都知道这可能是什么原因造成的？

- 编辑 -

我很确定这个问题是由artist_id为空的可能性引起的。但是，我无法阻止这种情况，所以我可以跳过行数为空的artist_id行吗？

解决方案

要遍历的节点不能为null！

这是一个泛型Hibernate错误消息，指出查询中的语法问题。作为另一个例子，忘记使用单词SELECT来启动select子句会产生相同的错误。在这种情况下，语法错误是由于on子句导致的 - HQL不支持它们。

  FROM track_history_items thi，artists art 
 WHERE thi.type =TrackBroadcast 
 AND thi.artist_id = art.id 
 GROUP BY art.name 
 ORDER thi.createdAt DESC 
  

I'm performing a SQL query through hibernate, which looks like:

SELECT thi 
FROM track_history_items thi 
JOIN artists art 
  ON thi.artist_id = art.id 
WHERE thi.type = "TrackBroadcast" 
GROUP BY art.name 
ORDER thi.createdAt DESC

but I'm getting the message that 'Node to traverse cannot be null!'. Anyone know what could be causing this?

--EDIT--

I'm pretty sure that this problem is being caused by the possibility of artist_id to be null. However, I can't prevent this, so can I just skip the rows track_history_item rows which have a null artist_id?

解决方案

node to traverse cannot be null!

This is a generic Hibernate error message indicating a syntax problem in your query. As another example, forgetting to start a select clause with the word "SELECT" would yield the same error.

In this instance the syntax error is due to the on clause - HQL does not support them. Instead do a cross join like so:

FROM track_history_items thi, artists art 
WHERE thi.type = "TrackBroadcast" 
AND  thi.artist_id = art.id 
GROUP BY art.name 
ORDER thi.createdAt DESC

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