Question

我的表格结构如下：

@Entity(tableName = "userFitnessDailyRecords")

public class UserFitnessDailyRecords {



    @NonNull
    @PrimaryKey
    private Date forDay;
    private int stepCount;
}

我写的用于获得总和和平均值的查询如下：

@Dao
public interface UserFitnessDailyRecordsDao {


    @Query("SELECT SUM(stepCount), AVG(stepCount) FROM userFitnessDailyRecords where forDay BETWEEN :startDay AND :endDay ORDER BY forDay ASC")
    UserFitnessDailyRecords getUserFitnessSumAndAverageForLastThirtyDays(Date startDay, Date endDay);


    @Query("DELETE FROM userFitnessDailyRecords")
    void deleteUserFitnessDailyRecord();

}

编译后，我收到错误，无法返回值，因为列不包含sum和average字段。在这种情况下，如何归还总和和平均值？

Answer 1

您正在从方法getUserFitnessSumAndAverageForLastThirtyDays（）返回UserFitnessDailyRecords条目。但是查询选择的列不会返回该类型的对象。

请记住在SQL查询中使用“AS”关键字来生成与POJO变量名称匹配的列名别名。

您可以从该方法返回POJO，也许是这样：

Kotlin方式：

data class SumAveragePojo(var total: Float, var average: Float)

Java方式：

class SumAveragePojo
{ 
    public float total;
    public float average;
}

并更改方法返回类型，如下所示：

@Query("SELECT SUM(stepCount) as total, AVG(stepCount) as average FROM userFitnessDailyRecords where forDay BETWEEN :startDay AND :endDay ORDER BY forDay ASC")
SumAveragePojo getUserFitnessSumAndAverageForLastThirtyDays(Date startDay, Date endDay);

使用房间

1 个答案: