数据库的基本表与存储文件之间通过建立( )之间的映像,保证数据的物理独立性。
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Iwasreallyanxiousaboutyou.You______homewithoutaword.
Basically,theseattitudesamounttoabelief________leisurecanandshouldbeputtogooduse
CollinsCOBUILDEnglishLanguageDictionary(1987)hassomeuniquefeaturessuchasdefinition,extracolumnand______.
Fishis________andexpensiveatthistimeoftheyearinthisarea.
AllplaysarealiketomejustasallmusicisaliketoTony.()