java 如何在没有直接链接到两个表的情况下对左外连接使用休眠条件
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How use hibernate criteria for a left outer join without direct link into the two tables
提问by
I'm trying to translate a SQL quest into Hibernate criteria.
我正在尝试将 SQL 任务转换为 Hibernate 标准。
My quest is working in SQL :
我的任务是在 SQL 中工作：
select * from objective
left outer join conditionstate
on objective.conditionid = conditionstate.conditionid
and conditionstate.personid = XXXX
where objective.toto_id = YYYYY
The objective is not directly mapped to the condition_state, but into a condition.
目标不是直接映射到条件状态，而是映射到条件。
objective --> condition <-- condition_state
I've tested something like :
我已经测试过类似的东西：
final DetachedCriteria criteriaObjective =
DetachedCriteria.forClass(Objective.class);
criteriaObjective.createAlias("conditionState", "conditionState", Criteria.LEFT_JOIN);
without success..
没有成功..
回答by ChssPly76
It's hard to suggest something without seeing your actual mappings. Going by your explanation and assuming that both condition and conditionState are mapped as many-to-one, you'd write something like:
如果没有看到您的实际映射，很难提出建议。根据您的解释并假设条件和条件状态都映射为多对一，您将编写如下内容：
final DetachedCriteria criteriaObjective =
DetachedCriteria.forClass(Objective.class);
criteriaObjective
.createCriteria("condition", Criteria.LEFT_JOIN)
.createCriteria("conditionState", Criteria.LEFT_JOIN)
.add(Restrictions.eq("personid", "XXXX") );
criteriaObjective.add(Restrictions.eqProperty("toto_id", "YYYY") );
Note that the above is NOTequivalent to the SQL query you've provided because "personid" condition will be generated as part of "WHERE" clause. As far as I know it's impossible to do a left join with condition using Criteria API - you may need to use HQL instead which provides with keywordfor that exact purpose:
请注意，上述内容不等同于您提供的 SQL 查询，因为“personid”条件将作为“WHERE”子句的一部分生成。据我所知，不可能使用 Criteria API 对条件进行左连接 - 您可能需要使用 HQL 来代替它为该确切目的提供关键字：
select o from objective as o
left join o.condition as c
left join c.conditionState as cs
with cs.person_id = 'XXXX'
and o.toto_id = 'YYYY'
