Question

我正在尝试为两个不同的设备进行成对测量，并在相同的时间戳上加入。在SQL中，这可以按预期工作：

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NHibernate.Hql.Ast.ANTLR.SemanticException:

Path expected for join!

如何指定同一个表的“路径”？

Answer 1

在HQL中，只能对实体之间的关联进行连接。如果你想要连接其他东西，唯一的可能是在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

加入的HQL路径（加入同一个表时）

1 个答案: