Spring JPA 中的属性 LIMIT 应该有什么？ SQL

Question

我正在尝试限制 nativeQuery = true，但 Spring JPA 找不到此查询。

我的错误是：

Caused by: java.lang.IllegalStateException: Using named parameters for method public abstract void se.danielmartensson.repositories.DataRepository.deleteByJobNameOrderByDateTimeLimit(java.lang.String,long,long) but parameter 'Optional[jobName]' not found in annotated query 'DELETE FROM Data data ORDER BY data.dateTime WHERE data.jobName =: jobName LIMIT firstIndex = :firstIndex, selectedSamples = :selectedSamples'!

所以我猜 LIMIT 应该有不同的属性，而不是 firstIndex 和 selectedSamples ？那会是什么呢？

我在 Spring Boot 中的 Repository 的查询在哪里

@Query(value = "SELECT * FROM Data data ORDER BY data.dateTime WHERE data.jobName = :jobName LIMIT firstIndex = :firstIndex, selectedSamples = :selectedSamples", nativeQuery = true)
List<Data> findByJobNameOrderByDateTimeLimit(@Param("jobName") String jobName, @Param("firstIndex") long firstIndex, @Param("selectedSamples") long selectedSamples);

@Modifying
@Query(value = "DELETE FROM Data data ORDER BY data.dateTime WHERE data.jobName =: jobName LIMIT firstIndex = :firstIndex, selectedSamples = :selectedSamples", nativeQuery = true)
void deleteByJobNameOrderByDateTimeLimit(@Param("jobName") String jobName, @Param("firstIndex") long firstIndex, @Param("selectedSamples") long selectedSamples);

Answer 1

我创建了一个使用H2 的示例项目。您必须更改您使用的数据库中的limit 和offset 部分。对于删除操作，定义了delete from table where id in (select id from table where .. order by .. limit .. offset ..)。

注意：Lombok 用于getter、setter 和toString。这不是必需的。

DataRepository.java

public interface DataRepository extends JpaRepository<Data, Integer> {
    @Query(value = "SELECT * FROM Data data WHERE data.jobName = :jobName ORDER BY data.dateTime limit :selectedSamples offset :firstIndex"
            , nativeQuery = true)
    List<Data>findByJobNameOrderByDateTimeLimit(@Param("jobName") String jobName, @Param("firstIndex") Integer firstIndex, @Param("selectedSamples") Integer selectedSamples);

    @Transactional
    @Modifying
    @Query(value = "DELETE FROM Data data WHERE data.id in (select id from Data d where d.jobName = :jobName order by d.dateTime limit :selectedSamples offset :firstIndex)"
            , nativeQuery = true)
    void deleteByJobNameOrderByDateTime(@Param("jobName") String jobName, @Param("firstIndex") Integer firstIndex, @Param("selectedSamples") Integer selectedSamples);
}

Data.java

@lombok.Data
@Entity
@Table
public class Data {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;

    @Column(name = "jobName")
    private String jobName;

    @Column(name = "dateTime")
    private LocalDateTime dateTime;

    public Data() {
    }

    public Data(String jobName, LocalDateTime dateTime) {
        this.jobName = jobName;
        this.dateTime = dateTime;
    }
}

测试

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.time.LocalDateTime;
import java.util.List;

@SpringBootTest
class DemoApplicationTests {
    @Autowired
    private DataRepository dataRepository;
    
    @Test
    void test1() {
        // insert dummy records
        dataRepository.save(new Data("job1", LocalDateTime.now().minusMinutes(1)));
        dataRepository.save(new Data("job1", LocalDateTime.now().minusMinutes(2)));
        dataRepository.save(new Data("job1", LocalDateTime.now().minusMinutes(3)));
        dataRepository.save(new Data("job1", LocalDateTime.now().minusMinutes(4)));

        // get records
        List<Data> dataList = dataRepository.findByJobNameOrderByDateTimeLimit("job1", 0, 4);
        for (Data data : dataList) {
            System.out.println(data);
        }

        // delete
        dataRepository.deleteByJobNameOrderByDateTime("job1", 1, 2);

        // get records
        dataList = dataRepository.findByJobNameOrderByDateTimeLimit("job1", 0, 4);
        for (Data data : dataList) {
            System.out.println(data);
        }
    }
}

输出

Hibernate: SELECT * FROM Data data WHERE data.jobName = ? ORDER BY data.dateTime limit ? offset ?

Data(id=4, jobName=job1, dateTime=2021-01-08T05:25:31.830)
Data(id=3, jobName=job1, dateTime=2021-01-08T05:26:31.829)
Data(id=2, jobName=job1, dateTime=2021-01-08T05:27:31.827)
Data(id=1, jobName=job1, dateTime=2021-01-08T05:28:31.756)

Hibernate: DELETE FROM Data data WHERE data.id in (select id from Data d where d.jobName = ? order by d.dateTime limit ? offset ?)

Hibernate: SELECT * FROM Data data WHERE data.jobName = ? ORDER BY data.dateTime limit ? offset ?

Data(id=4, jobName=job1, dateTime=2021-01-08T05:25:31.830)
Data(id=1, jobName=job1, dateTime=2021-01-08T05:28:31.756)

Mysql

对于mysql，使用以下脚本删除操作成功。

参考：MySQL DELETE FROM with subquery as condition - Answer

    @Transactional
    @Modifying
    @Query(value = "DELETE FROM Data WHERE id in (select id from (select id from Data where jobName = :jobName order by dateTime limit :selectedSamples offset :firstIndex) x)"
            , nativeQuery = true)
    void deleteByJobNameOrderByDateTime(@Param("jobName") String jobName, @Param("firstIndex") Integer firstIndex, @Param("selectedSamples") Integer selectedSamples);

Answer 2

如果您只想获取jobName 和firstIndex 和selectedSamples 匹配参数的行。您应该使用正确的 SQL 语法并将它们放入 where。

SELECT * FROM Data data
WHERE data.jobName = :jobName AND firstIndex = :firstIndex AND selectedSamples = :selectedSamples
ORDER BY data.dateTime

正确的语法是这样的：

select *
from [table]
where 'condiction'
order by [column]
limit [int]

---

LIMIT 但是用于设置 SQL 返回的最大元组，例如如果查询返回 10K 行但您只想查看前 5 行，则可以使用 limit 5 告诉 SQL 仅返回前 5 个 fetch .

同样在不同的 DBMS 中，可能需要使用不同的语法或方法来实现相同的目标，例如在 ORACLE 中我们没有limit 子句，而是使用FETCH 或简单地使用ROWNUM。