稠密索引：n20n稀疏索引：n100稠密索引：2nn5n(520i)(i=1i(520i)<=20)稀疏索引：n2n5n(520i)(i=1i(520i)<=20). = 1 GB3 ①500055000100(500010)20=1075 = 2 GB3 ②50005500020=1250b.最少的情况是5000个记录都为重复值所需块为：5000550001001=105
