【单选题】【消耗次数：1】
数据库系统中的三级模式以及模式间的映像提供了数据的独立性。下列关于两级映像的说法，正确的是（ ）。
①
外模式到模式的映像是由应用程序实现的，模式到内模式的映像是由DBMS实现的
②
外模式到模式的映像是由DBMS实现的，模式到内模式的映像是由应用程序实现的
③
外模式到模式的映像以及模式到内模式的映像都是由DBMS实现的
④
外模式到模式的映像以及模式到内模式的映像都是由应用程序实现的
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相关题目
【单选题】
数据库系统中的三级模式以及模式间的映像提供了数据的独立性。下列关于两级映像的说法，正确的是（ ）。
①
外模式到模式的映像是由应用程序实现的，模式到内模式的映像是由DBMS实现的
②
外模式到模式的映像是由DBMS实现的，模式到内模式的映像是由应用程序实现的
③
外模式到模式的映像以及模式到内模式的映像都是由DBMS实现的
④
外模式到模式的映像以及模式到内模式的映像都是由应用程序实现的
【简答题】
数据库系统提供的模式外模式映像实现了数据的[填空]独立性。
【简答题】
数据库系统的三级模式结构是指数据库系统是由[填空1]、内模式和外模式 三级构成。
【简答题】
数据库体系结构按照模式、[填空]和内模式三级结构进行组织。
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