Question

我遇到以下代码问题。我希望它从特定区域返回最大温度。区域有几个。我想两组之间的AND都是错误的。

select max(temperature)
from tempdat
group by tdate having tdate = curdate()
and group having zone having zone ='inne'

数据库有4个列，此查询只返回温度列，如何获取结果中的所有列？

Answer 1

select t1.zone_id,t1.temperature
   from tempdat t1
where
   t1.tdate = curdate()
and t1.temperature = 
   (select max(t2.temperature) from  tempdat t2 
        where t1.tdate = t2.tdate 
        and t1.zone_id = t2.zone_id);

Answer 2

每个日期的最大值 -

select max(temperature), tdate,zone
from tempdat
group by tdate, zone

如果您想要特定区域，请尝试每个日期

select max(temperature), tdate,zone
from tempdat where zone  ='inne'
group by tdate, zone

如果你想要每个区域的最大值和curr_date，

select max(temperature),zone
from tempdat
where tdate = curdate()
group by  zone

如果要应用过滤器，最好在WHERE子句中而不是在HAVING子句中应用它们。只有当您想对聚合数据应用过滤器时，才需要将它们放在HAVING子句中。

如何在一个查询中使用多个组？

2 个答案: