SQL：查询客户销售账本

Question

当特定用户支付现金时，插入下表

payments:
description     | Amount    | Date      |   custid 
cash            | 2000      | 2014-9-24 | 5
cash            | 3000      | 2014-9-26 | 5

特定用户购买产品时，插入下表

orders
Product         | qty   | amount  |  date      | custid
front light     |  2    |  3000   | 2014-9-22  | 5
back light      |  2    |  2500   | 2014-9-22  | 5

• 如果上述表格需要更改，也请指导我。？
• 是否需要支付表中的余额列。 ?
• 请记住，我是程序员而不是会计师，如果借记卡有任何错误，请告诉我。

我需要这个结果或类似的东西（客户的销售分类帐/客户帐户详细信息）。 SQL 查询是什么？

Product     | Debit  |  Credit      | Balance 
opening bal |        |              | 0
product     | 5500   |              | 5500
cash        |        | 2000         | 3500
cash        |        | 3000         | 500 

Answer 1

首先，您没有“open bal”的数据，所以我忽略了这一点。完全不清楚这是从哪里来的。

获取前三列（带日期）是将表连接在一起的问题。为此，union all 是最好的方法：

select *
from ((select custid, 'product' as product, date, sum(amount) as amount, -1 as dir
       from orders
       group by custid, date, amount
      ) union all
      (select custid, description, date, 1 as dir
       from payments
      )
     ) op;

接下来是添加累积件。在 MySQL 中，您可以使用变量来做到这一点：

select custid, product, date, amount,
       (@bal := if(@c = custid, @bal + amount * dir,
                   if(@c := custid, 0, 0)
                  )
       ) as bal
from ((select custid, 'product' as product, date, sum(amount) as amount, -1 as dir
       from orders
       group by custid, date, amount
      ) union all
      (select custid, description, date, amount, 1 as dir
       from payments
      )
     ) op cross join
     (select @c := -1, @bal := 0) vars
order by custid, date, dir desc