问题
单项选择题
数据库系统的核心是()。
A．编译系统
B．数据库
C．操作系统
D．数据库管理系统
答案
参考答案：D
解析：当局部的E-R图集成为全局的E-R图时，可能存在3种冲突：属性冲突、结构冲突、命名冲突。注意：逻辑冲突不属于局部E-R图集成为全局E-R图时存在的冲突，故选择A)。
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数据库系统的核心是()。
A．编译系统
B．数据库
C．操作系统
D．数据库管理系统
参考答案：D
解析：当局部的E-R图集成为全局的E-R图时，可能存在3种冲突：属性冲突、结构冲突、命名冲突。注意：逻辑冲突不属于局部E-R图集成为全局E-R图时存在的冲突，故选择A)。
| 完形填空。 It's said that many years ago clothes were made of animal skins. People started to wear clothes 1 they could keep themselves safe from the sun, wind, rain and cold. Today, we can use 2 materials (材料) to make different kinds of clothes. But clothes do 3 than keep us warm in modern society, and they can also 4 about our culture, our life, our jobs, our hobbies and even our mood (情绪). 5 , when we see a man in a uniform (制服), we know his 6 from the uniform. When we see a woman in a kimono (日本和服) , we may think that she is a _ 7 . If a man always wears sportswear, we may think he is _ 8 . and likes doing exercise. If a person __9 _ wears yellow or red clothes, maybe he or she is lively and easy-going. As the saying goes, "You are what you 10 ." | ||||
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