Question

这是我的工作数据库设置：

@Entity
class Foo {
    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Long id;

    @OneToMany(fetch = FetchType.LAZY)
    @JoinColumn(name = "FOO_ID")
    private Set<Bar> bars;

//...

}

@Entity
class Bar {
    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    private Long id;

    @Column(name = "STATUS")
    private String status;
    //...
}

FooRepository扩展了CrudRepository {

@Query("select distinct f from Foo f left join f.bars b where b.status = :status ")
public Page<Bar> findByBarStatus(@Param("status") BarStatus status, Pageable pageable);

}

我希望能够按Bar.status对此查询进行排序，以下是我尝试更改查询的方式：

@Query("select distinct f from Foo f left join f.bars b where b.status = :status order by b.status desc")
public Set<Bar> findByBarStatus(@Param("status") BarStatus status);

然而，这会导致sql语法错误：

org.h2.jdbc.JdbcSQLException: Order by expression "BARS1_.STATUS" must be in the result list in this case;

Answer 1

此处您已在f上应用了distinct，因此您不能按顺序使用其他列。实际上，逐项清单必须在选择列表中。

所以，问题出在查询中，如果您确定f将是唯一的（但事实并非我猜）或您可以尝试with子句，

with temp as  
(select distinct f, b.status 
 from Foo f left join f.bars b 
 where b.status = :status order by b.status desc) 
select f from temp

Answer 2

您必须在查询选择语句中调用b.status，如下面的查询。

    select DISTINCT(f), b.status from Foo f
 LEFT JOIN f.bars b where b.status = :status order by b.status desc

按关系属性排序

2 个答案: