Question

我试图在JPA中从本机查询中提取别名，类似于（SUM，COUNT），如果我完全拉动SUM或COUNT ，该方法可以返回整数（仅当我拉动它时）单独）。但我怎么能用剩下的物体把它拉出来？这是我想要做的样本

@Entity
@Table("hotels")

public class Hotel {
    @Column(name="id")
    @Id
    private int hotelId;

    @Column(name="hotel_name")
    private String hotelName;
    @OneToMany
    private List<Availability>list;

    private int avaialbeCount; //this one should be Aliased and need to be pulled by none column
}

存储库

public interface HotelRepository extends JpaRepository<Hotel,Integer>{
@Query(value="select h.*,a.count(1) as avaialbeCount from hotels h INNER JOIN availability a on (a.hotel_id=h.hotel_id) group by a.date",nativeQuery=true)
public List<Hotel> getHotels();

}

在上面的存储库中。我试图获得avaialbeCount与酒店列但我无法拉它，但我可以通过删除选择h。*拉它，并保持选择仅COUNT并使方法返回整数而不是酒店

Answer 1

您可以使用JPQL，类似这样的

@method_decorator(login_required, name='dispatch')
class ContactView(FormView):

要使用此@Query("SELECT new test.Hotel(h.hotelName, count(h)) FROM Hotel h GROUP BY h.hotelName")构造，您需要像

这样的构造函数

new test.Hotel(h.hotelName, count(h))

示例：

存储库：

public Hotel(String hotelName, Long avaialbeCount) { this.hotelName = hotelName; this.avaialbeCount = avaialbeCount; }

实体：

package test; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.Query; import org.springframework.stereotype.Repository; import java.util.List; @Repository public interface HotelRepo extends JpaRepository<Hotel, Long> { @Query("SELECT new test.Hotel(h.hotelName, count(h)) FROM Hotel h GROUP BY h.hotelName") List<Hotel> getHotelsGroupByName(); }

package test; import javax.persistence.*; @Entity @Table(name = "hotels") public class Hotel { @Id @Column(name = "id") @GeneratedValue(strategy = GenerationType.IDENTITY) private Long hotelId; @Column(name = "hotel_name") private String hotelName; @Transient private Long avaialbeCount; public Hotel() { } public Hotel(String hotelName) { this.hotelName = hotelName; } public Hotel(String hotelName, Long avaialbeCount) { this.hotelName = hotelName; this.avaialbeCount = avaialbeCount; } @Override public String toString() { return "Hotel{" + "hotelId=" + hotelId + ", hotelName='" + hotelName + '\'' + ", avaialbeCount=" + avaialbeCount + '}'; } }注释用于指示不在数据库中保留字段。

如何从JPA中的本机查询中提取别名

1 个答案: