A.候選索引B.主索引、候選索引、普通索引C.主索引或候選索引D.主索引、候選索引和唯一索引
A.COPY TO JRB.COPY FILE TO JRC.COPY STRU TO JRD.COPY STRU EXTE TO JR
A.數(shù)組B.層次C.二維表格D.矩陣