Question

我遇到了一个问题。

我搜索了几个小时，但没找到任何一个。

我想要做的是一个sql select，其中ORDER子句取决于列的值（因此它会针对每个元组进行更改）。

我设法通过HQL做到这一点：

SELECT NEW myDTO(m.id, m.name, " + calculDistance + " AS distance) FROM Table m GROUP BY m.mercId ORDER BY distance ASC

calculDistance取决于m.latitude和m.longitude

这很好用。但是，我的要求比这要复杂得多，而且对于阅读，更新等原因，我想直接用JPA来做。

你知道这是否可能吗？

感谢您的帮助。

修改

这是我的表结构的一部分（我只放了所需的列）：

@Entity
@Table(name = "td_merchant")
@XmlRootElement
@SequenceGenerator(name = "td_merchant_id_seq", sequenceName = "td_merchant_id_seq")
public class Merchant implements Serializable {

private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(generator = "td_merchant_id_seq", strategy = GenerationType.SEQUENCE)
@Column(name = "merc_id")
private Integer mercId;

@Column(name = "merc_name")
private String mercName;

@Column(name = "merc_latitude")
private Double mercLatitude;
@Column(name = "merc_longitude")
private Double mercLongitude;

...
}

Answer 1

I also faced same issue, i wrote one function which was taking input for order by as well as asc and desc seq.

public List<CompanyName> loadAllCompanies(CompanySortField sortField, boolean ascending) {

    String queryString = "select new com.Company(u.name, u.surname, " +
            " country.name, country.population, " +
            " city.name) from Company u left join u.city as city left join u.country as country " +
            " order by " + sortField.getField() + (ascending ? " asc " : " desc ");
    return entityManager.createQuery(queryString).getResultList();
}

您可以尝试这种方式，只需要触发另一个查询来查找公司排序字段。

JPA Hibernate。选择：ORDER子句取决于列的值

1 个答案: