Question

我正在使用Room Persistance Library（v2.0.0）查询POJO。我将所有这些实体都放在不同的表中（簿记，类别等）。我正在尝试将BookEntryEntity与与BookEntry的category_id相匹配的类别相结合。

class BookEntry(
        @Embedded var entity: BookEntryEntity = BookEntryEntity(),
        @Embedded(prefix = 'cg_') var category: Category? = null,
        contacts: List<Contact.ContactEntity>? = null
) : Parcelable {

    @Relation(
            entity = Contact.ContactEntity::class,
            parentColumn = 'id',
            entityColumn = 'bookentry_id'
    )
    var embeddedContacts: List<Contact.ContactEntity>? = contacts

    //...

    @Entity(tableName = 'bookentries')
    data class BookEntryEntity(
            @PrimaryKey(autoGenerate = true) @ColumnInfo(name = 'id') var id: Long = 0,
            @ColumnInfo(name = 'title') var title: String = "",
            @ColumnInfo(name = 'date') var date: Date = Date(),
            @ColumnInfo(name = 'value') var value: Double = 0.0,
            @ColumnInfo(name = 'notes') var notes: String = "",
            @ColumnInfo(name = 'entrytype') var entryType: Int = Type.Earning,
            @ColumnInfo(name = Reference.CATEGORY_ID) var categoryId: Long? = null
    )

}

嵌入实体Category不会自动加入。

@Entity(tableName = 'categories')
data class Category(@PrimaryKey(autoGenerate = true) @ColumnInfo(name = 'id') val id: Long = 0, @ColumnInfo(name = 'name') var name: String = "")

我尝试通过以下方式加入它：

@Dao
interface BookEntryDao {

    @Transaction
    @Query("SELECT * FROM bookentries INNER JOIN categories ON bookentries.cg_id = categories.id WHERE categories.id == bookentries.category_id ORDER BY bookentries.date DESC")
    fun getBookEntries(): LiveData<List<BookEntry>>
}

不幸的是，我遇到一个错误：

错误：查询存在问题：[SQLITE_ERROR] SQL错误或缺少数据库（无此列：bookentries.cg_id）

但是，如果我删除内部联接，则会收到以下警告：

警告：at.guger.moneybook.data.model.BookEntry有一些字段查询未返回的[cg_id，cg_name]。

如何正确加入查询？

Answer 1

尝试：

@Dao
interface BookEntryDao {

    @Transaction
    @Query("SELECT * FROM bookentries INNER JOIN categories ON bookentries.category_id = categories.id ORDER BY bookentries.date DESC")
    fun getBookEntries(): LiveData<List<BookEntry>>
}

将嵌入式实体的行加入Room Dao中的POJO

1 个答案: