在 HQL 查询中使用外连接
我正在尝试使用 HQL 和 OUTER JOIN 构建查询，但无法正常工作。考虑以下映射
<class name="Parent">
<id name="id" type="integer">
<generator class="native" />
</id>
</class>
<class name="Child">
<id name="id" type="integer">
<generator class="native" />
</id>
<many-to-one name="parent"/>
</class>
现在我想获得所有父母的列表以及父母的孩子的数量。假设我有一个有两个孩子的父母和一个根本没有孩子的父母。我期望像
+-------------------+
| parent | children |
+--------+----------+
| 1 | 2 |
| 2 | 0 |
+--------+----------+
使用 这样的输出普通 SQL 这根本不是问题，我会得到这个输出，执行类似的操作，
SELECT p.id as parent, count(c.id) as children from parents p LEFT OUTER JOIN children c on c.parent_id = p.id group by p.id;
但是使用 HQL 似乎不可能，因为在使用 a 时需要从父级到子级的路径 OUTER JOIN，我显然没有（也不想添加）
任何关于如何使用 HQL 使查询工作的想法还是真的 - 我简直不敢相信 -缺少休眠功能吗？
I'm trying to build a query using HQL and OUTER JOINs and just can't get it work. Consider the following mapping
<class name="Parent">
<id name="id" type="integer">
<generator class="native" />
</id>
</class>
<class name="Child">
<id name="id" type="integer">
<generator class="native" />
</id>
<many-to-one name="parent"/>
</class>
Now I"d like to get a list of all Parents and the amount of the Parents' children. Suppose I have one Parent with two children and one Parent with no children at all. I'd expect an output like
+-------------------+
| parent | children |
+--------+----------+
| 1 | 2 |
| 2 | 0 |
+--------+----------+
using plain SQL it isn't a problem at all, I'll get this output doing something like
SELECT p.id as parent, count(c.id) as children from parents p LEFT OUTER JOIN children c on c.parent_id = p.id group by p.id;
However it doesn't seem to be possible using HQL as one needs a path from Parent to Child when using a OUTER JOIN, which I obviously don't have (and also don't want to add).
Any ideas how to get the query working using HQL or is it really - I couldn't believe it - a missing hibernate feature?
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切换查询应该有帮助
Switching the query should help