如果是这样，语法是什么？
假设我希望Foo的一个实例与Bar的所有实例无关联：
在SQL它只是：
从FOO_BAR_MAPPING中删除
其中FOO_ID =？
在HQL中，我认为它会是这样的：
从Bar.foos删除foos
其中foos.id =：id
（其中foos是Foo的映射集合）
但似乎是错误的，给出：
org.hibernate.hql.ast.QuerySyntaxException：Bar.foos未映射
这对于HQL来说甚至是可能的吗？
解决方案为了回答您的具体问题，不，据我所知，这是不可能的HQL。
我认为你在这里混合SQL和HQL。在SQL中，你确实删除了记录，当然hibernate最终也会这样做。然而，Hibernate / HQL是以面向对象的思维模式设计的，所以在这种情况下的删除意味着你正在删除对象而不是关联。通常你会做如下的事情：
Foo f = session.get（Foo.class，id）;
f.getBars（）。clear（）;
session.merge（f）;
这将通过您指定的标识符来检索对象，并通过清除其集合来删除所有条形关联。很明显，你必须将Foo-Bars关联映射到正确的方向才能发挥作用。
And if so, what is the syntax?
Assume that I want an instance of Foo to be unassociated from all instances of Bar:In SQL it would simply be:
delete from FOO_BAR_MAPPING
where FOO_ID = ?
In HQL, I assumed it would be something like:
delete from Bar.foos foos
where foos.id = :id
(where foos is a mapped collection of Foo)
But appears to be wrong, giving:
org.hibernate.hql.ast.QuerySyntaxException: Bar.foos is not mapped
Is this even possible with HQL?
To answer your specific question, no, as far as I'm aware it's not possible with HQL.
I think you're mixing SQL and HQL a little bit here. In SQL, you indeed "delete" records, and of course hibernate will ultimately do that as well. However Hibernate/HQL is designed from an object-oriented mindset, so "delete" in this context means you are deleting objects, not associations. Typically you'd do something like follows:
Foo f = session.get(Foo.class, id);
f.getBars().clear();
session.merge(f);
This retrieves the object by the id you specified, and removes all Bar associations by clearing it's collection. Obviously you have to have the Foo-Bars association mapped in the proper direction for this to work.
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