Java JPA：需要多对多查询帮助

我有四个实体涉及到一个查询，我有点麻烦。关系如下：交易所--*合同--*联合体--*交易和简化实体如下：

@Entity
public class Exchange implements Serializable {
    @Id(name="EXCHANGE_ID")
    private long exchangeId;

    @Column
    private String exchangeShortName;
}


@Entity
public class Contract implements Serializable { 
        @Id
        private long contractId;

        @Column
        private String contractName;

        @ManyToOne
        @JoinColumn(name="EXCHANGE_ID")
        private Exchange exchange;

        @ManyToMany
        @JoinTable(name="CONTRACT_COMBO",
                        joinColumns = { @JoinColumn(name="CONTRACT_ID") },
                        inverseJoinColumns = {@JoinColumn(name="COMBO_ID")})
        private Set<Combo> combos;

        @Column(name = "ACTIVE_FLAG")
        private String activeFlag;
}

@Entity
public class Combo implements Serializable {

        @Id
        @Column(name="COMBO_ID")
        private Integer id;

        @ManyToMany
        @JoinTable(name="CONTRACT_COMBO",
                        joinColumns = { @JoinColumn(name="COMBO_ID") },
                        inverseJoinColumns = {@JoinColumn(name="CONTRACT_ID")})
        private Set<Contract> legs;

        @OneToMany(mappedBy = "combo")
        private Set<Trade> trades;    
}

@Entity
public class Trade implements Serializable {
        @Id
        @Column(name="TRADE_ID")
        private long tradeId;

        @Column(name="REFERENCE")
        private String reference;

        @ManyToOne
        @JoinColumn(name="COMBO_ID")
        private Combo combo;
}

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我想得到一份特定交易所的所有交易的清单，但我不能很好地与该交易所的会员合作。任何帮助都将不胜感激。

没有真正优化，但我认为这应该可以做到：

Long exchangeId = Long.valueOf(5324623L);
List<Trade> trades = em.createQuery("select T from Trade T where T in " +
    "(select distinct C from Combo c where c member of " +
        "(select e.combos from Exchange e where e.id = :id) " +
    ")").setParameter("id", exchangeId).getResultList();

试试这个

select distinct t 
  from Trade t
  join t.combo c
  join c.legs l
  join l.exchange e
 where e.exchangeShortName = 'whatever'

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差不多了，但我想你错过了合同的链接。