SUM内的条件

Question

我创建了以下查询，但我真正想要的是而不是SUM( credit - debit ) AS del 我需要SUM( credit - SUM of debit (Start Counting debit after transaction where description is 'Earned' ) AS del。 例如，从下面的查询我得到的借方值是在事务之前插入的，其中描述为'已获得'，并且我希望在事务'已获得'被插入表格后的SUM借记列

SQL小提琴链接：http://sqlfiddle.com/#!2/12e46/4

    SELECT user_id, 'Removed', 0, SUM( credit - debit ) AS del, 0, NOW( ), NOW( ) 
FROM accounts
WHERE created
BETWEEN DATE_SUB( DATE( NOW( ) ) , INTERVAL DAYOFWEEK( NOW( ) ) +6
DAY ) 
AND DATE_SUB( DATE( NOW( ) ) , INTERVAL DAYOFWEEK( NOW( ) ) -1
DAY ) 
AND (
description LIKE  '%Earned%'
OR description =  'S'
OR description =  'B'
)
GROUP BY user_id
HAVING del > 0