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我在 Oracle 数据库中有如下表：

| GROUP | SEQ | OTHER_DATA |
|-------|-----|------------|
| 1     | 1   | ~~~~~~~~~~ |
| 1     | 2   | ~~~~~~~~~~ |
| 1     | 3   | ~~~~~~~~~~ |
| 2     | 1   | ~~~~~~~~~~ |
| 2     | 2   | ~~~~~~~~~~ |
| 2     | 3   | ~~~~~~~~~~ |

whereGROUP是外键，(GROUP, SEQ)是主键。我想为第 1 组插入下一条记录，应该是(1, <(MAX SEQ FOR GROUP 1) + 1>, <OTHER DATA>) = (1, 4, <OTHER DATA>).

我正在使用 Spring Boot 2。到目前为止，我有以下内容：

public class MyEntityPK implements Serializable {
    private Long group;
    private Long seq;
    // getters and setters ...
}

@Entity
@Table(name = "MY_TABLE")
@IdClass(MyEntityPK.class)
public class MyEntity {

    @Id
    private Long group;

    @Id
    private Long seq;

    @ManyToOne
    @JoinColumn(name="GROUP", insertable=false, updatable=false)
    private Group group;

    private String otherData;
    // getters and setters ...
}

public interface MyEntityRepository extends CrudRepository<MyEntity, MyEntityPK> {}

当我明确设置该seq字段时，如下例所示，一切正常。

@RunWith(SpringRunner.class)
@SpringBootTest
public class MyEntityTest {

    @Autowired
    MyEntityRepository repository;

    @Test
    public void testSaveMyEntityWithExplicitParameters() {
        MyEntity entity = new MyEntity();
        Group group = new Group(1L, "Group description");
        entity.setGroup(group);
        entity.setSeq(4L);
        repository.save(entity);
    }
}

但是我不知道如何在持久层中增加序列，而不向MyEntityRepository用于获取最大 seq 值并显式设置它的服务添加逻辑。我不能@GeneratedValue与序列生成器一起使用，因为它会在不考虑组的情况下生成下一个可用值。

4

1 回答 1

1

作为建议，您可以尝试使用触发器，请查找原始示例：

CREATE OR REPLACE TRIGGER seq_upd_before_insert
BEFORE INSERT
   ON MY_TABLE
   FOR EACH ROW
DECLARE
   v_seq number;
BEGIN
   -- Find max seq for performing INSERT into your table
   SELECT max(seq) INTO v_seq 
   FROM MY_TABLE
   WHERE group = :new.group
   GROUP BY group;

   -- Update new seq field to max seq + 1 before insert
   :new.seq := v_seq + 1;
END;
/

希望能帮助到你

于 2020-01-09T09:50:21.030 回答