关系操作的特点是()操作。
参考答案:集合
解析:
在关系操作中,所有操作对象与操作结果都是关系。关系定义为元数相同的元组的集合。因此,关系操作的特点是集合操作。
判断题。(正确的打“√”,错误的打“×”)
1.小数的位数越多,这个小数就越大。[ ]
2.读小数时,整数部分和小数部分都按照整数的读法来读。 [ ]
3.0.6和0.60大小相同,计数单位不相同。[ ]
4.5.19在自然数5和6之间,它近似于5。 [ ]
5.0.496保留两位小数是0.5。 [ ]
根据句意和首字母或汉意完成单词。
1. —What would you do if you had a million dollars? —I'd give it to c_________.
2. Pandas are Mary's f_________ animals.
3. He finds watching movies f_________ because the people speak too quickly.
4. I'm t_________ (害怕) of the dark, so I never go out in the evening.
5. There is a s_________ (奇怪的) smell in the room. Do you know what it is?
6. You have to be 18 years old before you are a_________ to drive a car.
7. Did you know potato chips were i_________ by mistake?
8. If you study hard, I'm sure you will s_________.
9. The librarian has put the library books on those s_________ neatly; you can find the book you want easily.
10. What would you do if you i_________ your knee while running?