【单选题】根据《税收征收管理法》规定,纳税人如在一定期限内发现其缴纳的税款超过应纳税额的,可以向税务机关要求退还多缴的税款并加算银行同期存款利息。这里的一定期限内是指( )。
【单选题】--- You’ve left the water running. --- Oh, I have. _______ and turn it off.
【单选题】从关系 R 中选择出若干属性运算是( )
【单选题】选择运算(σ):σF(R)={t|t∈R∧F(t)=TRUE} 选择运算是对一个二维表按条件F进行横向选择,从R中选择出若干元组(行),其中F是一个逻辑表达式,其值为“真”或“假”,如“课号=“C12”∧成绩>80”可以用检索选修了G12课程并且成绩大于80分的学生数据。投影运算(π):πA(R)={t[A]|t∈ R}投影运算是对一个二维表进行纵向筛选,从R中选择出若干属性列,组成新的关系,其中...
C.
σR.C=S.C((πA,B R)×(πD S))
D.
σR.C=S.C(πD((πA,B R)×S)
【判断题】学会了编制年计划、月计划、周计划的方法,坚持有计划地安排近期日程,有助于生涯措施的落实和目标的实现。
【单选题】听力原文:M: Does this bill belong to you? W: Oh thanks, I've just lost five pounds. M: I'm glad that I've found the owner, otherwise I would have to go to the Lost and Found. Why does the woman thank the ...
A.
He lent her some money.
B.
He gave her a five-pound bill.
C.
He returned her money found.
【单选题】选择运算σF(R)是
C.
是从两个关系的笛卡儿积中选取属性间满足一定条件的元组
【单选题】听力原文:M: I'm about worn out. I've been busy at the office and I've got a stiff neck and sore shoulders. Guess I'm getting old. W: Don't be silly. You just need a good rest. Q: What's the man's real pro...
A.
He has a serious disease.
【简答题】已知二次函数y=3x 2 -8x+4; (1)该函数图象与x轴有几个交点; (2)试说明一元二次方程3x 2 -8x+4=7的根与二次函数y=3x 2 -8x+4的图象间的关系。 (3)试问x为何值时,函数y的值为-1。
【简答题】从关系中找出满足给定条件的元组的操作称为 ,而 运算是对关系的垂直分解,它是在关系R中选择出若干个属性组成新的关系