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【简答题】
已知f(t)，为求f(t 0 -at)应按下列哪种运算求得正确结果(式中t 0 ，a都为正值)?
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反馈参考答案：
举一反三
【简答题】A．пsname(S)D∞ σPno='P3'(SPJ) B．пsname(SD∞ σPno='P3'(SPJ)) C．пsname(S)-пsname(σPno≠'P3'(S∞(SPJ) D．пsname(S)-пsname((S∞σPno≠'P3'，(SPJ)
【判断题】a和b等价 (a)if (count % 10 == 0) newLine = true; else newLine = false; (b)newLine = (count % 10 == 0);
A.
正确
B.
错误
【单选题】现有学生关系表S(sno,sname,ssex,sage),下列选项中 与关系代数表达式 Π sno,sname (S) 等价的 SQL 语句是 ________ 。
A.
select * from S where sno, sname;
B.
select from S where sno, sname;
C.
select sno, sname from S where *;
D.
select sno, sname from S;
【简答题】A．Πsname(S)-Πsname(σPno≠'P3'(S∞(SPJ) B．Πsname(S)—nsname((S∞σPno≠'P3'(SPJ) C．Πsname(S)D∞σPno＝'P3'(SPJ) D．Πsname(SD∞σPno＝'P3'(SPJ))
【单选题】听力原文：W: You must have forgotten the meeting. I didn't see you last night. M: Everybody says that to me and they think I have a bad memory. In fact I would have come to the meeting if I had known about...
A.
He has forgotten the meeting.
B.
He has a bad memory.
C.
He didn't get the message about the meeting.
D.
He didn't want to attend the meeting.
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