Question

我有以下实体类

public class Customer {
    @Id
    private int id;
    @Column(name = "CID")
    private String cid;
}


public class Alccs {
    @Id
    private int vid;
//    @Column(name = "CID")
//    private String cid;

    @ManyToOne
    @JoinColumn(name = "CID", referencedColumnName = "CID")
    private Customer customer;
}


public class Rtwo {
    @Id
    private int jobNo;

    @ManyToOne
    @JoinColumn(name = "CID", referencedColumnName = "CID")
    private Customer customer;
}




public class RTwoCycle {
    @Id
    private int cycleJobNo;
    @Column
    private int vid;

    @ManyToOne
    @JoinColumn(name = "JobNo", referencedColumnName = "JobNo")
    private TblRtwo tblRtwo;

}

如何使用HQL和criteria编写类似以下的查询

select top 20 * from RTwoCycle rtCycle join Alccs al on rtCycle.vid = al.vid;

对于HQL，我尝试关注

from TBLRTwoCycle rtCycle join TBLAL al on rtCycle.vid = al.vid

但出现QuerySyntaxException: Path expected for join!错误

关于标准，我不知道怎么做

该怎么做？

Answer 1

早于5.1的JPA和Hibernate版本需要定义的关系才能在JPQL查询中连接两个实体。这通常会导致级联JOIN语句以遍历实体之间的关系图，或者导致如果实体之间没有关系，则无法使用JPQL进行实体JOIN的语句。

Hibernate 5.1引入了对不相关实体的显式联接。语法与SQL非常相似，可让您在ON语句中定义JOIN条件。

More Info

Answer 2

from RTwoCycle as rtCycle inner join Alccs as al with rtCycle.vid = al.vid

Answer 3

对于HQL的简单连接，on clause就足够了

from table1 as t1 inner join table2 as t2 on t1.vid=t2.vid

或

from table1 as t1, table2 as t2 where t1.vid=t2.vid

标准Restriction.sqlRestriction是此问题的解决方案

session.createCriteria(Class1,"c1")
        .createAlias("class2", "c2")
        .add(Restrictions.sqlRestriction("c1.vid=c2.vid")

没有直接连接的休眠联接查询

3 个答案: