我有一列'hour‘我有一列'kind’(它可以是1,2或3)SELECT count(id), SUM(hour) as totHour, SUM( IF ( kind =1, 1, 0 ) ) as countKindOneSELECT count(id), SUM(hour) as totHour, COUNT( IF ( kind = 1 ) ) as countKindOne但是mysql告诉我我有一个错误.
在C#中执行SQL语句并将所有数据分组是很容易的,但是这使得C++作业有点无用,而且它可能是细粒度的 select a = exp(sum(log(x))),b = exp(sum(log(x))), d = exp(sum(log(z))),
e = exp(sum(log-Again,在C#中执行这条语句并只返回分组的元素很容易,但这意味着在C#中已经完成了sum()和