在 Spring Boot/JPA 查询语言中实现复杂的 MAX 函数

Question

Spring Boot 在此处使用 JPA/Hibernate 和 CrudRepository impls 来管理我的数据库表的持久性。

我有以下 MySQL 表：

CREATE TABLE IF NOT EXISTS price_scarcity_configs (
    price_scarcity_config_id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    price_scarcity_config_ref_id VARCHAR(36) NOT NULL,
    price_scarcity_config_version BIGINT NOT NULL,
    price_scarcity_config_updated_on DATETIME NOT NULL,
    price_scarcity_config_fizz INTEGER NOT NULL,

    CONSTRAINT pk_price_scarcity_configs PRIMARY KEY (price_scarcity_config_id),

    CONSTRAINT uc_price_scarcity_configs_ref_id_and_version UNIQUE (price_scarcity_config_ref_id, price_scarcity_config_version)
);

这些记录将被版本化，并且“相同”记录的不同版本都将共享相同的price_scarcity_config_ref_id。因此，2+ 条记录可以具有相同的price_scarcity_config_ref_id，但会有两个截然不同的不同版本。

我还使用以下 JPA/Hibernate 实体对其进行建模：

// Uses Lombok annotations to generate getters/setters, etc.

@MappedSuperclass
@Data
@EqualsAndHashCode(callSuper=false)
public abstract class BaseEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String refId;

}

@Entity
@Table(name = "price_scarcity_configs")
@AttributeOverrides({
        @AttributeOverride(name = "id", column = @Column(name = "price_scarcity_config_id")),
        @AttributeOverride(name = "refId", column = @Column(name = "price_scarcity_config_ref_id"))
})
@Data
@EqualsAndHashCode(callSuper=false)
public class PriceScarcityConfiguration extends BaseEntity {

    @Column(name = "price_scarcity_config_version")
    private Long version;

    @Column(name = "price_scarcity_config_updated_on")
    private Date updatedOn;

    @Column(name = "price_scarcity_config_fizz")
    private Integer fizz;

}

我现在正在尝试编写PriceScarcityConfigurationRepository 并且需要一个相当复杂的查询。给定refId，我需要找到匹配该 ref id 并且具有最高/最大版本号的记录。执行此操作的原始 SQL 查询是：

select
  *
from
  price_scarcity_configs pcs
inner join
  (
    SELECT
      price_scarcity_config_ref_id,
      MAX(price_scarcity_config_version) as max_ver
    FROM
      price_scarcity_configs
    group by
      price_scarcity_config_ref_id
  ) t
on
  t.price_scarcity_config_ref_id = pcs.price_scarcity_config_ref_id 
  and
  t.max_ver = pcs.price_scarcity_config_version;

鉴于我的存储库并使用 JPA/Hibernate 的内置查询语言/annos，我该如何实现此查询？

public interface PriceScarcityConfigurationRepository extends CrudRepository<PriceScarcityConfiguration,Long> {

    @Query("FROM PriceScarcityConfiguration WHERE ??? HOW TO IMPLEMENT THE ABOVE QUERY HERE ???")
    PriceSheetConfiguration fetchLatestVersionByRefId(@Param("refId") String refId);

}

Answer 1

您可以改用以下查询并使用setMaxResults(1)

FROM PriceScarcityConfiguration p WHERE p.refId = :refId ORDER BY p.version DESC

或者简单地使用 Spring Data 表示法

List<PriceSheetConfiguration> findFirstByRefIdOrderByVersionDesc(String refId);