mysql - 如何获得正确的最小值和最大值

Question

我有以下结构http://sqlfiddle.com/#!9/f8341c 从这些记录中，我的预期输出如下

Name|MinCost |MaxCost | Open | Close | Date
ABC |13.6    | 15.3   | 14.1 | 14.2  | 2015-12-02
DEF |93.2    | 96.3   | 93.7 | 95.4  | 2015-12-02 
ABC |15.1    | 15.6   | 15.1 | 15.2  | 2015-12-03
DEF |97.2    | 97.7   | 97.7 | 97.7  | 2015-12-03

现在我已经做到了

SELECT t1.name as 'Name',t1.min as 'MinCost',t1.max as 'MaxCost',t2.open ,t3.close,t1.times as 'Date'
  FROM(
        select name, max(cost) as 'max',min(cost) as 'min', date(time) as 'times'  
        from providers 
        group by  times,name 
        order by times
   ) AS t1
   JOIN (
     select name,cost as 'open',  time  
     from providers 
     where TIME(time) = '00:00:00'   
     group by time,name
     order by time
   ) as t2 on t1.name=t2.name
   JOIN (
       select name,cost as 'close', time  
       from providers 
       where TIME(time) = '23:59:59'   
       group by time,name
       order by time
   ) as t3 on t2.name=t3.name 
   GROUP BY t1.times,t1.name
   ORDER BY t1.times,t1.name

这给了我以下输出

| Name | MinCost | MaxCost | open | close |       Date |
|------|---------|---------|------|-------|------------|
|  ABC |    13.6 |    15.3 | 14.1 |  14.2 | 2015-12-02 |
|  DEF |    93.2 |    96.3 | 97.7 |  95.4 | 2015-12-02 |
|  ABC |    15.1 |    15.6 | 14.1 |  14.2 | 2015-12-03 |
|  DEF |    97.2 |    97.7 | 97.7 |  95.4 | 2015-12-03 |

我需要什么来更正查询？

Answer 1

因为你的名字不是唯一的，你需要在 join on 子句中添加 time 这样你就可以用 name 得到一个唯一的值和时间。

下面的查询应该有效，Demo on your fiddle得到预期的输出

  SELECT t1.name as 'Name',t1.min as 'MinCost',t1.max as 'MaxCost',t2.open ,t3.close,t1.times as 'Date'
  FROM(
        select name, max(cost) as 'max',min(cost) as 'min', date(time) as 'times'  
        from providers 
        group by  times,name 
        order by times
   ) AS t1
   JOIN (
     select name,cost as 'open',  date(time) as 'times' 
     from providers 
     where TIME(time) = '00:00:00'   
     group by time,name
     order by time
   ) as t2 on t1.name=t2.name and t1.times = t2.times
   JOIN (
       select name,cost as 'close', date(time) as 'times' 
       from providers 
       where TIME(time) = '23:59:59'   
       group by time,name
       order by time
   ) as t3 on t2.name=t3.name  and t2.times = t3.times
   GROUP BY t1.times,t1.name
   ORDER BY t1.times,t1.name