找出每行的最大值:
select 行主键,max(ntemp)
from (select 行主键,nTemp02 as nTemp from 气象要素表
union select 行主键,nTemp08 as nTemp from 气象要素表
union select 行主键,nTemp14 as nTemp from 气象要素表
union select 行主键,nTemp20 as nTemp from 气象要素表
) a
group by 行主键
select 行主键,max(ntemp)
from (select 行主键,nTemp02 as nTemp from 气象要素表
union select 行主键,nTemp08 as nTemp from 气象要素表
union select 行主键,nTemp14 as nTemp from 气象要素表
union select 行主键,nTemp20 as nTemp from 气象要素表
) a
group by 行主键
解决方案 »
免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货