连接所需的 HQL 路径（连接同一个表时）

发布于 2024-12-02 04:28:10 字数 674 浏览 1 评论 0原文

我正在尝试获取两个不同设备的测量对，并在相同的时间戳上连接。在 SQL 中，这按预期工作：

select
  leftItem.Timestamp, leftItem.Value, rightItem.Value
from
  DataTable leftItem
  inner join DataTable rightItem
  on leftItem.Timestamp = rightItem.Timestamp
where
  leftItem.Device = 1 and rightItem.Device = 2

但如果我尝试将其转换为 HQL：

select
  left, right 
from
  DataTable as left 
  inner join DataTable as right
  on left.Timestamp = right.Timestamp
where
  left.Device = 1 and right.Device = 2

我得到一个 NHibernate.Hql.Ast.ANTLR.SemanticException:

Path expected for join!

How do I specify a “path” to the same table ？

原文

I am trying to get pairs of measurement for two different devices, joined on equal Timestamps. In SQL, this works as expected:

select
  leftItem.Timestamp, leftItem.Value, rightItem.Value
from
  DataTable leftItem
  inner join DataTable rightItem
  on leftItem.Timestamp = rightItem.Timestamp
where
  leftItem.Device = 1 and rightItem.Device = 2

But if I try to convert it to HQL:

select
  left, right 
from
  DataTable as left 
  inner join DataTable as right
  on left.Timestamp = right.Timestamp
where
  left.Device = 1 and right.Device = 2

I get a NHibernate.Hql.Ast.ANTLR.SemanticException:

Path expected for join!

How do I specify a "path" to the same table?

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像极了他 2024-12-09 04:28:10

在 HQL 中，连接只能在实体之间的关联上完成。如果您想要连接其他内容，唯一的可能性是在 where 子句中进行连接：

select left, right 
from
  DataTable as left, DataTable as right
where
  left.Timestamp = right.Timestamp
  and left.Device = 1 
  and right.Device = 2

In HQL, joins can only be done on associations between entities. If you want a join on something else, the only possibility is to make the join in the where clause:

select left, right 
from
  DataTable as left, DataTable as right
where
  left.Timestamp = right.Timestamp
  and left.Device = 1 
  and right.Device = 2

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