A system field should only be used as an operand at a read position if its content is not set by the same statement.
如果语句不设置一个系统字段的值，则它只能作为一个读取位置的操作数来使用。
A system field should only be used as an operand at a read position if its content is not set by the same statement.
如果语句不设置一个系统字段的值，则它只能作为一个读取位置的操作数来使用。
应用推荐