総勘定元帳のクレジット、借方＆残高はどのように計算できますか？

Question

バランスが適正値が表示されない

のMySQLデータベーステーブル：テーブルの

CREATE TABLE `transactions` (
    `trx_id` int(11) NOT NULL AUTO_INCREMENT, 
    `trx_type` enum('debit','credit') DEFAULT NULL, 
    `trx_amount` float DEFAULT NULL, 
    `trx_description` mediumtext NOT NULL, 
    `trx_date` date NOT NULL, 
    `purpose_id` int(11) NOT NULL, 
    `staff_id` int(11) DEFAULT NULL, 
    `admin_id` int(11) NOT NULL, 
    `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, 
    `updated_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, 
    PRIMARY KEY (`trx_id`) 
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8; 

/*データtransactions */

insert into `transactions`(`trx_id`,`trx_type`,`trx_amount`,`trx_description`,`trx_date`,`purpose_id`,`staff_id`,`admin_id`,`created_at`,`updated_at`) 
values (1,'credit',100,'annual tour','2016-01-01',2,7,2,'2016-11-24 10:28:35','2016-11-29 12:21:08'), 
(2,'debit',200,'Product Sale','2016-11-19',6,5,2,'2016-11-24 10:33:02','2016-11-29 12:21:12'), 
(3,'debit',250,'Product Sale','2016-11-19',6,4,2,'2016-11-24 10:33:11','2016-11-29 12:21:43'), 
(4,'credit',300,'Product Sale','2015-01-27',6,4,2,'2016-11-24 10:33:14','2016-11-29 12:21:53'), 
(5,'credit',450,'Product Sale','2016-01-29',5,2,2,'2016-11-24 10:33:17','2016-11-29 12:21:58'), 
(6,'debit',210,'Product Sale','2016-11-19',6,4,2,'2016-11-24 10:33:20','2016-11-29 12:22:17'), 
(7,'credit',350,'Internal','2016-11-30',14,3,1,'2016-11-24 13:04:04','2016-11-29 12:22:28'); 

MySQLのクエリ：

SELECT trx_id,staff_id 
    , SUM(COALESCE(CASE WHEN trx_type = 'debit' THEN trx_amount END,0)) total_debits 
    , SUM(COALESCE(CASE WHEN trx_type = 'credit' THEN trx_amount END,0)) total_credits 

    , SUM(COALESCE(CASE WHEN trx_type = 'debit' THEN trx_amount END,0)) 
    - SUM(COALESCE(CASE WHEN trx_type = 'credit' THEN trx_amount END,0)) balance 
    FROM erp_transactions GROUP BY staff_id HAVING balance <> 0 ORDER BY trx_id; 

出力結果：

Answer 1

select s.*, 
     s.debit - s.credit as Balance, 
     @RunningBalance:= @RunningBalance + s.debit - s.credit RunningBalance 
from 
(
select min(trx_id) trx_id,t.staff_id, 
    sum(case when trx_type = 'debit' then trx_amount else 0 end) as Debit, 
    sum(case when trx_type = 'credit' then trx_amount else 0 end) as Credit 
from trans t 
group by staff_id 
order by trx_id 
) s, 
(Select @RunningBalance:=0) rb 
order by s.trx_id 

結果

+--------+----------+-------+--------+---------+----------------+ 
| trx_id | staff_id | Debit | Credit | Balance | RunningBalance | 
+--------+----------+-------+--------+---------+----------------+ 
|  1 |  7 |  0 | 100 | -100 |   -100 | 
|  2 |  5 | 200 |  0 |  200 |   100 | 
|  3 |  4 | 460 | 300 |  160 |   260 | 
|  5 |  2 |  0 | 450 | -450 |   -190 | 
|  7 |  3 |  0 | 350 | -350 |   -540 | 
+--------+----------+-------+--------+---------+----------------+