SQL 到 JPQL，如何查询嵌套的 JPQL

Question

我想知道 JPQL 是否可以嵌套查询。我在学习Spring Data JPA，也上传了几个相关的问题。

如果我在 MySQL 中有以下 sql，我如何生成 JPQL：

select
    c.*
from
    cheat c
    left join (select * from cheat_vote where val = 1) v on c.cheat_seq = v.cheat_fk
group by
    c.cheat_seq
having
    count(*) < 10
limit 5

我有两个实体。

public class Cheat implements Serializable{

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "cheat_seq", length = 10)
    private Long cheatSeq;

    @Column(name = "question", unique = true, nullable = false)
    private String question;

    @Column(name = "answer", unique = true, nullable = false)
    private String answer;

    @Column(name = "writer_ip", nullable = false)
    private String writerIP;

    @Temporal(TemporalType.TIMESTAMP)
    @Column(name = "reg_date", nullable = false)
    private Date regDate;

    @Transient
    private String regDateText;

    @OneToMany(mappedBy = "cheat", fetch=FetchType.LAZY)
    private Set<CheatVote> vote;

    @Override
    public String toString() {
        return "Cheat [cheatSeq=" + cheatSeq + "]";
    }


}

Above 实体有一个@OneToMany 集合，集合实体在下面。

public class CheatVote implements Serializable{

    private static final long serialVersionUID = 1L;

    @GeneratedValue(strategy=GenerationType.IDENTITY)
    @Id
    @Column(name="seq", nullable=false)
    private Long seq;

    @Column(name="val", nullable=false)
    @NonNull
    private Integer value;

    @Column(name="ip_address", nullable=false)
    @NonNull
    private String ipAddress;

    @JoinColumn(name="cheat_fk", referencedColumnName="cheat_seq")
    @ManyToOne(cascade=CascadeType.ALL, fetch=FetchType.LAZY)
    @NonNull
    private Cheat cheat;

    @Override
    public String toString() {
        return "CheatVote [seq=" + seq + "]";
    }


}

我想要获得少于 10 个子 CheatVote 实体的 Cheat 实体。

Answer 1

你可以试试：

@Query("SELECT c FROM Cheat c LEFT JOIN c.vote v WHERE v.value = 1 GROUP BY c.cheatSeq HAVING count(c) < 10")

关于'LIMIT'你可以使用Spring Data JPA的参数Pageable