mysql - 计算特定日期范围内MySQL中每行值的百分比

Question

我想获取mysql数据库中某个表的某个日期范围内具有最大值的前4行。所以我可以用这个代码行来做，例如:

SELECT MONTH(date) as month, amount from sales where date >='2014-01-01' AND date <='2014-12-31' ORDER BY amount DESC LIMIT 4

但我想添加一个包含每个值百分比的新列，我尝试使用这一行:

SELECT MONTH(date) as month, amount, round(amount*100/sum(amount) ,1) as 'percent' from sales where date >='2014-01-01' AND date <='2014-12-31' ORDER BY `amount` DESC LIMIT 4

但它不起作用。我怎么才能得到它？我需要一些帮助。

Answer 1

这是一种方法。提供原始数据片段也有帮助。创建 sql fiddle帮助更多!!

select month, amount, round(amount*100/total,1) as percent
  from 
  (
    select MONTH(date) as month, amount 
      from sales 
      where date >='2014-01-01' AND date <='2014-12-31'
     ORDER BY amount DESC LIMIT 4
  ) c JOIN (
    select sum(amount) as total
      from sales 
      where date >='2014-01-01' AND date <='2014-12-31'
  ) t