如何在Hibernate查询语言中执行左连接？ [英] How to perform left join in Hibernate Query Language?

问题描述

Hql查询：

$ b $这是我的HQL查询，但它不起作用并且发生错误。 b

  SELECT 
 * 
 FROM 
 TABLEA A 
 LEFT JOIN 
 A.TABLEB B 
 WHERE 
 A.COLUMNNAME = B.COLUMNAME 
  

并导致此错误：

  org.hibernate.QueryException：
此查询捕获异常。无法解析TABLEB：TABLEA的属性： 
  

我该如何解决这个问题？其实我从多个表中检索到一个值。此查询不适用于 CreateQuery（strQuery） 。

解决方案

仅在主实体中使用LEFT JOIN：

样本

EntityA具有EntityB类型的对象entityB所以你可以

  SELECT A FROM实体A LEFT JOIN A.entityB B WHERE ... 
  
 
 
 
 b 
 
  SELECT A FROM实体A LEFT JOIN实体B B WHERE B.entityA = A 
  
，因为您有错误。这是一个尚未解决的Hibernate问题。
 
This is my HQL query, but it isn't working and is throwing an error.

Hql query:
SELECT 
    *
FROM 
    TABLEA A 
LEFT JOIN 
    A.TABLEB B 
WHERE 
    A.COLUMNNAME = B.COLUMNAME
and it causes this error:
org.hibernate.QueryException:
This Query caught Exception. could not resolve property: of TABLEB:TABLEA.
How can I solve this problem? Actually I retrieved a value from more than one table. This query doesn't work with CreateQuery(strQuery).
解决方案
In HQL you can use LEFT JOIN only with linked property in main entity:

Sample 

EntityA has an object entityB of type EntityB so you can
SELECT A FROM EntityA A LEFT JOIN A.entityB B WHERE ...
IF EntityA haven't entityB property but is EntityB have a property entityA, you can't write this:
SELECT A FROM EntityA LEFT JOIN EntityB B WHERE B.entityA = A 
because you have an error. This is an Hibernate issue not resolved yet.

                        
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