MySQL的条件语法在SELECT

Question

我有这样的表，命名奖励：

+----+------------+-----------+----------+-------------+ 
| id | product_id | sell_what | get_what | valid_until | 
+----+------------+-----------+----------+-------------+ 
| 1 | 1001  | 10  | 10000 | 15 nov 2015 | 
| 2 | 1002  | 7   | 12000 | 31 dec 2015 | 
| 3 | 1003  | 12  | 100000 | 31 dec 2015 | 
+----+------------+-----------+----------+-------------+ 

，而且我有这个表，命名user_earned：

+----+---------+------------+-----------+------------------+ 
| id | user_id | product_id | sell_what | transaction_date | 
+----+---------+------------+-----------+------------------+ 
| 1 | 609  | 1003  | 1   | 2 Nov 2015  | 
| 2 | 220  | 1001  | 12  | 3 Nov 2015  | 
| 3 | 609  | 1003  | 1   | 20 Nov 2015  | 
| 4 | 910  | 1001  | 2   | 21 Nov 2015  | 
| 5 | 910  | 1001  | 3   | 21 Nov 2015  | 
| 6 | 910  | 1001  | 8   | 22 Nov 2015  | 
+----+---------+------------+-----------+------------------+ 

我也有这个疑问来总结sell_what号基于user_id：

SELECT user_id, product_id, 
SUM(sell_what) AS sold, 
MAX(transaction_date) AS transaction_date 
FROM user_earned 
GROUP BY user_id, product_id 

和这里的结果：

+---------+------------+-----------+------------------+ 
| user_id | product_id | sold  | transaction_date | 
+---------+------------+-----------+------------------+ 
| 220  | 1001  | 12  | 3 Nov 2015  | 
| 609  | 1003  | 2   | 20 Nov 2015  | 
| 910  | 1001  | 13  | 22 Nov 2015  | 
+---------+------------+-----------+------------------+ 

现在，问题是...如何加入这一结果与表的奖励，让我得到了表是这样的：

+---------+------------+-----------+-------------------+ 
| user_id | product_id | sold  | remaining_balance | 
+---------+------------+-----------+-------------------+ 
| 220  | 1001  | 12  | 2     | 
+---------+------------+-----------+-------------------+ 

用户609是不可见的，因为他只有2级销售的产品，而产品1003的最低报酬为12

，因为他的最新产品1001 TRANSACTION_DATE是2015年11月22日910用户是不可见的，而奖励有效期至11月15日2015年

如何应用这种合作nditional到一个SQL语法？谢谢。

Answer 1

我想你想要这种要求？

select * , 
    (t.sold - r.sell_what) as remaining_balance 
from reward as r 
inner join (
    SELECT user_id, product_id, 
    SUM(sell_what) AS sold, 
    MAX(transaction_date) AS transaction_date 
    FROM earned_incentive 
    GROUP BY user_id, product_id 
    ) as t 
    on r.product_id = t.product_id 
WHERE 
    r.sell_what <= t.sold 
    and t.transaction_date <= r.valid_until 

检查SQL Fiddlesqlfiddle http://sqlfiddle.com/images/fiddle_transparent_small.png