Question

我需要从两个不同的表中选择数据。每天的数据和计数分布，例如：

customers | sales | date
5         |   5   | 2014-11-01
0         |   2   | 2014-11-02
1         |   0   | 2014-11-03
0         |   0   | 2014-11-04

并一直持续到月底

我开始选择这种方式，但不知道如何在每天搜索并且不想在循环中进行多次搜索

  SELECT (SELECT COUNT(*) FROM customers) AS customers, 
           (SELECT COUNT(*) FROM sales) AS sales 
  FROM dual

Answer 1

假设每个表中都有一个日期列，您可以接近：

select date, sum(customers) as customers, sum(sales) as sales
from ((select date, count(*) as customers, 0 as sales
       from customers
       where date between '2014-11-01' and '2014-11-30'
       group by date
      ) union all
      (select date, 0 as customers, count(*) as sales
       from sales
       where date between '2014-11-01' and '2014-11-30'
       group by date
      )
     ) cs
group by date
order by date;

这将为您提供任何一个表中的所有日期。要获取所有日期，即使是那些没有数据的日期，您需要一个日期表或生成它们的方法。假设您有一个日历表，这是一种方法：

select date, sum(customers) as customers, sum(sales) as sales
from ((select date, 0 as customers, 0 as sales
       from calendar
       where date between '2014-11-01' and '2014-11-30'
      ) union all
      (select date, count(*) as customers, 0 as sales
       from customers
       where date between '2014-11-01' and '2014-11-30'
       group by date
      ) union all
      (select date, 0 as customers, count(*) as sales
       from sales
       where date between '2014-11-01' and '2014-11-30'
       group by date
      )
     ) dcs
group by date
order by date;

从两个不同的表中选择数据，每天计数和分配

1 个答案: