检查 Room DB 中的列是否为 NULL 或为空

Question

我想获取MyModel其deletedAt值为的列表NULL。这是我的表：

@Entity(tableName = "my_table")
data class MyModel(
    @PrimaryKey
    @ColumnInfo(name = "id")
    var id: String,
    @ColumnInfo(name = "deletedAt")
    var deletedAt: Date? = null
)

道：

@Dao
abstract class MyDao : BaseDao<MyModel> {

@Query("SELECT * from my_table WHERE deletedAt IS NULL")
abstract fun getList(): LiveData<List<MyModel>>
}

我的类型转换器：

object DateTypeConverter {
@TypeConverter
@JvmStatic// It need to added else gives unwanted data binding error :D
fun fromTimestamp(value: Long?): Date? {
    return if (value == null) null else Date(value)
}

@TypeConverter
@JvmStatic
fun dateToTimestamp(date: Date?): Long? {
    return date?.time
}

但即使某些条目的 deletedAt 值为空，它也会返回所有 MyModel 数据。

Answer 1

尝试使用以下NULLIF检查null或empty喜欢

NULLIF(deletedAt, '') IS NULL

完整的Query是

@Query("SELECT * from my_table WHERE NULLIF(deletedAt, '') IS NULL")