数据库的产品很多，尽管它们支持的数据模型不同，使用不同的数据库语言，而且数据的存储结构也各不相同，但体系结构基本上都具有相同的特征，采用“三级模式和两级映像”，如下图所示，图中①、②、③分别表示数据库系统中（ ），图中④、⑤、⑥分别表示数据库系统中（ ）。
问题1选项
A.物理层、逻辑层、视图层
B.逻辑层、物理层、视图层
C.视图层、物理层、逻辑层
D.视图层、逻辑层、物理层
问题2选项
A.外模式/内模式映射、外模式/内模式映射、概念模式/内模式映射
B.外模式/概念模式映射、外模式/概念模式映射、概念模式/内模式映射
C.概念模式/内模式映射、概念模式/内模式映射、外模式/内模式映射
D.外模式/内模式映射、外模式/内模式映射、概念模式/外模式映射
正确答案及解析
正确答案
解析
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