表结构如下:
id
Macid
Value
HappenTime
在表中求出:Macid, Max(Value) as 最大值, HappenTime as 最大值对应时刻,
Min(Value) as 最小值,HappenTime as 最小值对应时刻 那位高手帮忙给一下写法,或思路
id
Macid
Value
HappenTime
在表中求出:Macid, Max(Value) as 最大值, HappenTime as 最大值对应时刻,
Min(Value) as 最小值,HappenTime as 最小值对应时刻 那位高手帮忙给一下写法,或思路
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from biao
where biao.value=(select max(value) from biao)另外一个一样
access2000是可以的,不知你用的是什么。
我看可能不行吧,放在两条纪录中肯定没问题。
用
union
select macid,value as 最小值,happentime as 最小值对应时刻
from biao
where biao.value=(select min(value) from biao)
select macid,max(value) as 最大值,happentime as 最大值对应时刻,value as 最小值,happentime as 最小值对应时刻
from biao
where biao.value in (select max(value) from biao union select min(value))
group by value
select macid,max(value) as 最大值,happentime as 最大值对应时刻,value as 最小值,happentime as 最小值对应时刻
from biao
where biao.value in (select max(value) from biao a union select min(b.value) from biao b)
group by value
(select max(value) from biao tmp1 ) as 最大值,
(select happentime from biao tmp2 where value=(select max(value) from biao tm1 )) as 最大值对应时刻,
(select min(value) from biao tmp3 ) as 最小值,
(select happentime from biao tmp4 where value=(select min(value) from biao tm2)) as 最小值对应时刻
from biao 不过没什么效率
这样是不是效率很低,不过这到是我要的答案,因为我还要用macid分组以及限定查询时间段,哇,这样不累死才怪。
有没有更好一点的办法
(Select min(value) from biao) as 最小值,happentime as 最大值对应时刻 ,
(Select happentime from biao where value=min(value))as 最小值对应时刻
from biao