Question

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）（2，4,5,6）（8，9，10）

用group by 能分组吗，怎么分
假设还有一个字段 num，要用group by 统计三个分组的num值的和，怎么写。

Answer 1

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 else 0 end),
sum(case when num in (2,4,5,6) then num else 0 end),
sum(case when num in (8,9,10) then num else 0 end)
from tb group by num

试验下这个