SQL在单个表

Question

下表包含借记或贷记“操作”。我想从客户那里找到平衡：

CLIENT_ID | ACTION_TYPE | ACTION_AMOUNT
10        | credit      | 100$ 
10        | debit       |  62$
10        | credit      |  62$

基于此代码：Using MySQL to calculate balances from debits and credits in a single table

SELECT client_id
 , SUM(COALESCE(CASE WHEN action_type = 'debit' THEN action_amount END,0)) total_debits
 , SUM(COALESCE(CASE WHEN action_type = 'credit' THEN action_amount END,0)) total_credits
 , SUM(COALESCE(CASE WHEN action_type = 'debit' THEN action_amount END,0)) 
 - SUM(COALESCE(CASE WHEN action_type = 'credit' THEN action_amount END,0)) balance
 FROM my_table 
 WHERE CLIENT_ID = 10
 GROUP  
    BY client_id
HAVING balance <> 0;

fowling代码给出了结果：Ballance -100，它是正确的但是在财务方面它是错的;

让我们分析一下行动：

1 -> customer gives payment in advance 100$ (credit)
2 -> customer invoice 62$ (debit)
3 -> customer pays invoice 62$ (credit) 
4 -> ballance is -38$ not -100$

如何获得正确的Ballance，重新设计“Action”表或SQL代码？设置 - 信用没有帮助。

感谢您的帮助和时间。