SQL：查詢客戶銷售臺賬

Question

當特定的用戶支付現金，插下表中

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

特定當用戶購買產品，下表中插入

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

• 還指導我如果上面的表格需要改變。
• 是付款表中任何需要餘額的列。 ？
• 請記住，我是一名程序員沒有會計，如果有任何錯誤的借記卡讓我知道。

我需要這個結果或類似的東西（客戶/客戶帳戶詳細信息的銷售分類帳）。什麼是SQL查詢？

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

Answer 1

首先，您沒有「open bal」的數據，所以我忽略了這一點。完全不清楚這是從哪裏來的。

獲取前三列（帶日期）是將表連接在一起的問題。爲此，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; 

接下來是添加累計片。在MySQL中，你會這樣做使用變量：

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