亚非国家的民族问题有相当一部分是源于欧美帝国主义殖民体系的遗留问题。
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建立索引需要额外的存储代价,但使用索引扫描一定比简单的全表扫描效率要高。
A. 对
B. 错
关系数据库管理系统查询处理4个阶段的执行顺序为( )
A. 查询检查、查询分析、查询优化、查询执行
B. 查询检查、查询优化、查询分析、查询执行
C. 查询分析、查询优化、查询检查、查询执行
D. 查询分析、查询检查、查询优化、查询执行
Hello, everybody! On behalf of the hotel, I’d like to express our warmest welcome to you. We do hope all our (1)____________will feel happy and comfortable here. We would be pleased to provide (2)__________ services to meet your needs. Here you can find many convenient facilities for you to use, such as a (3)_________, a healthy club and an indoor swimming poor. We also have three restaurants (4)_________ Chinese and Western foods, two bars and a large shopping center. Any suggestions for (5)_______ our service are welcome. Thank you for your attention.
Ladies and gentlemen, our plane is flying smoothly now. The duty- free sales will soon begin. Please (1)_____________ your list of purchase. In your seat pocket, you can find the Shopping on Board magazine, All prices are listed both in the local currency and in US dollars. And you can pay (2)__________ or by using a credit card. We accept (3)_________ major credit cards. Frequent passengers win points (4)_________ on board. There are some excellent bargains and there are several items specially designed for our (5)___________. Thank you.