下图说明了层次降维的效果。它将长方体的数目从2^n减少到n+1通过这种降维，我想知道下面的查询如何给出正确答案？选择b，按b从x组中计数（1）选择c，按c从x组中计数（1）从x中选择b，c，count（1）按b，c分组
bybem2ql1#
看来我找到了答案：=>意味着等于
group by A,B => group by A,B group by B,C => group by C => group by A,B,C group by A,C => group by C => group by A,B,C group by A => group by A group by B => group by A,B group by C => group by A,B,C group by B,C => group by A,B,C
1条答案
按热度按时间bybem2ql1#
看来我找到了答案：=>意味着等于