【简答题】The way that Addison continues his study will make the other____________________.
【简答题】A.Dr Richardson is content with Mary's essay. B.Dr Richardson is disappointed with Mary's essay. C.Mary has great difficulties in completing the essay. D.Mary can complete the essay by the deadline.
【单选题】西门子MM420变频器可外接开关量,输入端⑤~⑦端作多段速给定端,可预置()个不同的给定频率值。
【单选题】西门子MM420变频器可外接开关量,输入端5~7端作为段速给定端,可预置( )个不同的给定频率值。
【单选题】西门子MM420变频器可外接开关量,输入端5~7端作多段速给定端,可预置( )个不同的给定频率值。
【单选题】下列说法错误的是( )。
A.
唯一性约束用于保证表中某个字段的值不重复且值能为空( null),一个表可以定义多个唯一性约束。
C.
定义主键约束的关键字是foreign key。
D.
MySQL中不能删除非空约束,但可以取消非空约束。
【单选题】Pull up your car.Do not___the fire engine!
【单选题】The first speaker of this meeting is ______.
【单选题】The style. of 'Visitors would make their way at once to the upper floor by way of the staircase.' is______.
【单选题】This is Mary Allen Brown. She is a doctor. You can call her ______. [ ]