求助SQL语句
表A中有如下字段date num
2007-4-1 0:00:00 6
...
2007-4-1 15:00:00 15
...
2007-4-1 21:00:00 24
..
....
....
2007-4-30 0:00:00 15
..
2007-4-30 15:00:00 21
.....
2007-4-30 21:00:00 30
我只列出0,15,21这三个时段的,实际上每个小时都有数据.
我想查询出每天哪个时段的总NUM数最多,哪个时段的总NUM数最少.
即:想得到
date total_num
2007-4-1 0:00:00 6
2007-4-1 21:00:00 24
....
2007-4-30 0:00:00 15
2007-4-30 21:00:00 30
请问如何写这个SQL语句,谢谢! select date,sum(num)
from a
group by 1
order by 1 desc
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