在学生借书数据库中，已有“学生”表和“借阅”表，其中“学生”表含有“学号”、“姓名”等信息，“借阅”表含有“借阅编号”、“学号”等信息。若要找出没有借过书的学生记录，并显示其“学号”和“姓名”，则正确的查询设计是
A．
B．
C．
D．
参考答案：A
解析： 本题考查的是查询设计。首先，要找出没有借书记录的学生，在查询设计器中的“学号”列下的“条件”行中键入Is Null。其次，由于只显示“学号”和“姓名”，所以要取消来自“借阅”表“学号”列“显示”行中的复选框。
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| Mobile phones are everywhere in big cities. It seems that 1 can survive without one. Mobile phones are a great 2 to stay connected with friends and family. 3 , it is important to remember that there are certain times 4 you should not be using your phone, especially as a student, during school. 5 you are in class, you should not be sending your friends text messages 6 taking phone calls. Your classmates and teacher should not have to deal with this rude 7 . Aren't you at school to learn? In the United States, students would never be allowed to 8 their mobile phones during class. If you were to send or 9 a text message you would probably be kicked 10 class. It is very disturbing to hear a lot of tones and ringing during 11 . There are many more rules for mobile phone use in America and it is to 12 respect for those around you. As a teacher in China, I have to 13 students using mobile phones every day. I have told my class to 14 their phones, but many students do not listen. The 15 to be connected all the time seems to be more 16 than the desire to learn. It's easy to understand 17 it is so tempting(诱惑人的)to have your phone on during class. It seems so easy just to send a short text message; it's not hurting anyone, is it? But you may actually be hurting 18 when you do this. Your teacher knows when you use your phone and may give you a 19 grade. Sending a text message also takes your attention away from what's going on in class, you may 20 something important. | ||||
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