空状态 meaning in English

dummy status
idle state

This feature allows value types to have an uninitialized , or empty , state similar to how reference types can be set to null
此功能允许将值类型设置为未初始化状态（即空状态），这与将引用类型设置为
If the table was nonempty before the bulk import operation , the cost of revalidating the constraint may exceed the cost of applying check constraints to the incremental data
如果在大容量导入操作之前表为非空状态，则重新验证约束的开销可能超过将check约束应用于增量数据的开销。