select sum(aaa)/count(1) from glxw group by datepart(yyyy,sj),datepart(mm,sj),datepart(dd,sj),datepart(hh,sj)
or
select datepart(yyyy,sj),datepart(mm,sj),datepart(dd,sj),datepart(hh,sj),
avg(aaa) from glxw group by datepart(yyyy,sj),datepart(mm,sj),datepart(dd,sj),datepart(hh,sj)