SQL中用Group by 分组 假如有个字段ID,值1~10,想分成3组(1,3,7)(2...答:select id,sum(case when id in (1,3,7) then 1 else 0 end),sum(case when id in (2,4,5,6) then 1 else 0 end),sum(case when id in (8,9,10) then 1 else 0 end)from tb group by id 这个意思?---补充--- select num,sum(case when id in (1,3,7) then num ...