我使用Spring Data JPA并定义了一个原生SQL查询，旨在基于特定条件检索给定客户（KLIENCI）的单个CPC记录。然而，该查询返回CPC记录列表而不是单个记录，这不是预期的行为。
下面是SQL查询供参考：

@Query(value = "SELECT k.ID_KLIENT, k.NAZWA, k.EMAIL,  \n" +
        "\tc.ID_CPC , c.DATA_ROZLICZENIA, c.ID_MASZYNA, \n" +
        "\tm.ID_MASZYNA, m.MODEL, m.KOLOR  \n" +
        "FROM KLIENCI k \n" +
        "JOIN CPC c ON c.ID_KLIENT = k.ID_KLIENT \n" +
        "JOIN MASZYNY m ON m.ID_KLIENT  = k.ID_KLIENT AND m.ID_MASZYNA = c.ID_MASZYNA \n" +
        "WHERE c.DATA_ROZLICZENIA = (\n" +
        "\tSELECT MAX (c2.DATA_ROZLICZENIA)\n" +
        "\tFROM CPC c2 \n" +
        "\tWHERE  c2.ID_KLIENT  = k.ID_KLIENT AND c2.ID_MASZYNA = c.ID_MASZYNA \n" +
        ") AND k.ID_KLIENT = :customerId",
        nativeQuery = true)
List<CustomerEntity> findCPCsForCustomer(@Param("customerId") int customerId);

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下面是results在 DBeaver 中的样子：
然而，Spring创建了3个查询而不是一个，并返回指定客户的所有CPC：

Hibernate: 
    SELECT
        k.ID_KLIENT,
        k.NAZWA,
        k.EMAIL,
        c.ID_CPC ,
        c.DATA_ROZLICZENIA,
        c.ID_MASZYNA,
        m.ID_MASZYNA,
        m.MODEL,
        m.KOLOR   
    FROM
        KLIENCI k  
    JOIN
        CPC c 
            ON c.ID_KLIENT = k.ID_KLIENT  
    JOIN
        MASZYNY m 
            ON m.ID_KLIENT  = k.ID_KLIENT 
            AND m.ID_MASZYNA = c.ID_MASZYNA  
    WHERE
        c.DATA_ROZLICZENIA = (
            SELECT
                MAX (c2.DATA_ROZLICZENIA)  
            FROM
                CPC c2   
            WHERE
                c2.ID_KLIENT  = k.ID_KLIENT 
                AND c2.ID_MASZYNA = c.ID_MASZYNA  
        ) 
        AND k.ID_KLIENT = ?
Hibernate: 
    select
        x1_0.id_klient,
        x1_0.id_maszyna,
        x1_0.kolor,
        x1_0.model 
    from
        maszyny x1_0 
    where
        x1_0.id_klient=?
Hibernate: 
    select
        c1_0.id_klient,
        c1_0.id_cpc,
        c1_0.data_rozliczenia,
        c1_0.id_maszyna 
    from
        cpc c1_0 
    where
        c1_0.id_klient=?

型

客户类别

public class CustomerEntity {

    @Id
    @Column(name = "ID_KLIENT")
    private int id;

    @Column(name = "NAZWA")
    private String name;
    private String email;

    @JsonManagedReference
    @OneToMany(mappedBy = "customerEntity", fetch = FetchType.LAZY)
    private List<XeroEntity> xeroEntityList;

    @JsonManagedReference
    @OneToMany(mappedBy = "customerEntity", fetch = FetchType.LAZY)
    private List<CPCEntity> cpcEntityList;
}

型

Xero机器类

public class XeroEntity {

    @Id
    @Column(name = "ID_MASZYNA")
    private int id;

    private String model;

    @Column(name = "KOLOR")
    private String color;

    @JsonBackReference
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "ID_KLIENT")
    private CustomerEntity customerEntity;
}

型

CPC类

public class CPCEntity {

    @Id
    @Column(name = "ID_CPC")
    private int id;

    @Column(name = "ID_MASZYNA")
    private int xeroId;
    @Column(name = "DATA_ROZLICZENIA")
    private Date settlementDate;

    @JsonBackReference
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "ID_KLIENT")
    private CustomerEntity customerEntity;

}

型
此外，我尝试使用JPQL来解决这个问题，但遇到了同样的问题。
我已确认数据库架构正确，预期结果是特定客户的每台计算机有一条CPC记录。但是，查询返回多条CPC记录。我不确定为什么会发生这种情况，我正在寻找有关如何修改查询或存储库方法以按预期返回一条CPC的指导。