Question

我想选择国家，其中一个人和 最旧/原始国家。 < / p>

此示例有2个表：

PERSON 包含个人信息及其当前国家/地区
HISTORY 与此人的历史国家/地区。它们按ID排序（所以我没有为这个简单的例子添加日期）。

我在SQL中使用这样的东西：

SELECT p.COUNTRY, h.HISTORY
FROM COUNTRY AS c, HISTORY as h
WHERE c.ID = h.PERSON
AND h.ID = (SELECT MIN(h2.ID) FROM HISTORY as h2 WHERE h2.ID = name.ID)

我应该如何使用JPA执行此操作？（实体对象在我的问题的最后）。

SELECT p.country, p.historyEntity.history
FROM PersonEntity AS p
WHERE MIN(p.historyEntity.id)

谢谢！欢迎任何建议。

Table: PERSON
ID    |    Name    |   COUNTRY
------------------------------
1     |    John    |   USA
2     |    Maria   |   CANADA
3     |    Peter   |   FRANCE

Table: HISTORY
ID    | PERSON (FK)|   HISTORY
------------------------------
1     |    1       |   MEXICO
2     |    1       |   BRASILIA
3     |    1       |   USA
4     |    2       |   GERMANY
5     |    2       |   CANADA
6     |    3       |   JAPAN
7     |    3       |   KOREA
8     |    3       |   USA


@Table(name = "PERSON")
public class PersonEntity {
    @Id
    @Column(name = "ID")
    private long id;
    @Column(name = "NAME")
    private String name;
    @Column(name = "COUNTRY")
    private String country;
    @OneToMany(mappedBy = "historyEntity")
    private Set<HistoryEntity> historyEntities = new HashSet<HistoryEntity>(0);

...
}

@Table(name = "HISTORY")
public class HistoryEntity {
    @Id
    @Column(name = "ID")
    private long id;
    @ManyToOne()
    @JoinColumn(name = "PERSON")
    private PersonEntity personEntity;
    @Column(name = "HISTORY")
    private String history;

...
}

Answer 1

我想你知道你的查询不起作用......试试这个：

SELECT p.country, h.history
FROM PersonEntity AS p
JOIN p.historyEntity h
WHERE h.id IN (SELECT MIN(h2.id) FROM HistoryEntity h2 where h2.historyEntity=p GROUP BY historyEntity)

如何从JPA的连接表中选择最小值？

1 个答案: