Question

我想要一个查询来获取按天分组的最大值和最小值之间的差异。我的尝试不起作用：

SELECT date(`date`), 
   (max(value) - min(value)) as value,
FROM `sub_meter_data` 
where date(sub_meter_data.date) > '2012-10-01' 
  and sub_meterID in('58984','58985','58986','58987')
group by date(`date`);

每个sub_meter的值可能大于3000，但仅相差＆lt;每天10个。我想要差异，即结果＆lt; 10。通过上面的查询，我得到了结果＆gt; 3000。

下面的查询，只选择一个仪表，并给出正确的结果，最大值（17531），最小值（17523）和差值（8）。

SELECT date(sub_meter_data.date) as date,
   max(value) as max_meter,
   min(value) as min_meter, 
   max(value) - min(value) as diff,
FROM `sub_meter_data`
where date(sub_meter_data.date) > '2012-10-01' 
  and sub_meterID in('57636')
  group by date(sub_meter_data.date)

但是在in子句中添加另一个仪表，给出一个不好的结果，最大值是17531，最小值是3021，差值是14510.但是我想要每米的差值，然后加在一起。

SELECT date(sub_meter_data.date) as date,
   max(value) as max_meter,
   min(value) as min_meter, 
   max(value) - min(value) as diff,
   FROM `sub_meter_data`
where date(sub_meter_data.date) > '2012-10-01' 
  and sub_meterID in('57636', '57628')
  group by date(sub_meter_data.date)

我尝试过的另一种尝试是：

SELECT date(sub_meter_data.date) as date,
   sum(CASE WHEN sub_meterID = '57628' OR sub_meterID = '57636' THEN (max(value) -     min(value)) ELSE 0 END) as value
   FROM `sub_meter_data`
where date(sub_meter_data.date) > '2012-10-01'

Answer 1

查询仅按天（日期）进行分组，但您还要按米进行分组，因此您需要将其添加到group by：

select sub_meterID, date(`date`) as day, max(value) - min(value) as value
from `sub_meter_data`
where date(`date`) > '2012-10-01'
    and sub_meterID in ('58984','58985','58986','58987')
group by sub_meterID, date(`date`);

然后，如果你想按天加总差异，你可以这样做：

select day, sum(diff) as total_diff
from (
    select sub_meterID, date(`date`) as day, max(value) - min(value) as diff
    from `sub_meter_data`
    where date(`date`) > '2012-10-01'
       and sub_meterID in ('58984','58985','58986','58987')
    group by sub_meterID, date(`date`)
    ) a
group by day

或者如果你想按米计算：

select sub_meterID, sum(diff) as total_diff
from (
    select sub_meterID, date(`date`) as day, max(value) - min(value) as diff
    from `sub_meter_data`
    where date(`date`) > '2012-10-01'
       and sub_meterID in ('58984','58985','58986','58987')
    group by sub_meterID, date(`date`)
    ) a
group by sub_meterID

MySQL在选择行的最大值和最小值之间得到差异

1 个答案: