如何使用LEFT OUTER JOIN创建JPA查询 [英] How to create a JPA query with LEFT OUTER JOIN

问题描述

我开始学习JPA，并基于我在SQL Server中测试的以下本机SQL实现了JPA查询示例：

I am starting to learn JPA, and have implemented an example with JPA query, based on the following native SQL that I tested in SQL Server:

SELECT f.StudentID, f.Name, f.Age, f.Class1, f.Class2 
FROM Student f 
    LEFT OUTER JOIN ClassTbl s ON s.ClassID = f.Class1 OR s.ClassID = f.Class2
WHERE s.ClassName = 'abc'

来自上面的SQL我构建了以下JPQL查询：

From the above SQL I have constructed the following JPQL query:

SELECT f FROM Student f LEFT JOIN f.Class1 s;

如你所见，我仍然缺少条件或s.ClassID =来自我原始查询的f.Class2 。我的问题是，如何将它放入我的JPQL？

As you can see, I still lack the condition OR s.ClassID = f.Class2 from my original query. My question is, how can I put it into my JPQL?

推荐答案

写这个;

 SELECT f from Student f LEFT JOIN f.classTbls s WHERE s.ClassName = 'abc'

因为您的学生实体与ClassTbl实体有一对多的关系。

Because your Student entity has One To Many relationship with ClassTbl entity.

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