Question

所以我在MySQL中有一个表PowerUse。它有两个重要的列，ID（long int）和timeRecorded（timeStamp）。条目之间通常存在长时间差距。我的目标是查询表格以获得结果告诉我20分钟内每分钟有多少记录 - 包括0分钟没有记录的分数。

感谢MySQL: Select All Dates In a Range Even If No Records Present我已经得到了下面的查询，但是我无法让这件事情发挥作用。有人能指出我正在制造的明显错误，所以我可以不停地撞击砖墙吗？我知道它在JOIN中，我只是看不到它。谢谢！

select count(PowerUse.id) + 0 as counter, timestamp((PowerUse.timeRecorded  div 100)*100) as time
from  PowerUse right join    
(
select date_add(NOW(), INTERVAL -n2.num*10-n1.num MINUTE) as dateb from
(select 0 as num
   union all select 1
   union all select 2
   union all select 3
   union all select 4
   union all select 5
   union all select 6
   union all select 7
   union all select 8
   union all select 9) n1,
(select 0 as num
   union all select 1
   union all select 2
 ) n2
 as ) datea 

 on (timestamp(PowerUse.timeRecorded  div 100)*100)  = dateb.datea 
   group by timeRecorded div 100 ;

Answer 1

我猜您最好的选择是创建另一个表：

start_date
END_DATE

并用你的范围填充....

然后你可以加入：

select start_date, count(PowerUse.id) + 0 as counter, timestamp((PowerUse.timeRecorded  div 100)*100) as time
from  PowerUse 
right join timeframes on (  timestamp((PowerUse.timeRecorded  div 100)*100) >= start_date and timestamp((PowerUse.timeRecorded  div 100)*100) < end_date )
group by start_date

像这样的东西

SQL JOIN语法问题

1 个答案: