• 我试图在房间数据库中使用@Relation从三个表中实现关系，但与它混淆。
• DB由学生、科目和成绩表组成。
• 学生表 *：

@Entity(tableName = "student")
data class Student(
    @PrimaryKey(autoGenerate = false)
    @ColumnInfo(name = "student_id")
    var id: Int = 0,
    @ColumnInfo(name = "student_name")
    var name: String? = null,
    @ColumnInfo(name = "student_email")
    var email: String? = null,
    @ColumnInfo(name = "student_created_date")
    var created: Long = System.currentTimeMillis(),
    var school_id: Int = -1
)

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• 主题表 *：

@Entity(tableName = "subject")
data class Subject(
    @ColumnInfo(name = "subject_id")
    var id: Int,
    @ColumnInfo(name = "subject_name")
    var name: String
)

型

• 标记表 *：

@Entity(tableName = "marks")
data class Marks(
    @ColumnInfo(name = "student_id")
    var stu_id: Int,
    @ColumnInfo(name = "subject_id")
    var sub_id: Int,
    @ColumnInfo(name = "marks")
    var marks: Int,
)

型
我想按科目检索学生及其各自的分数。下面是我定义的类，但我不知道如何用three tables定义关系：

data class StudentWithMarks(
    @Embedded var student: Student,
    @Relation(
        parentColumn = "student_id",
        entityColumn = "student_id"
    )
    var marks: List<Marks>
)

型