更新下一行中的值 MYSQL

Question

我应该查询什么来更新下一个 ROW2 等等，这些将从上一行中扣除。

更新 tbl SET BAL= ''

第 1 行有 10 个 QTY 和 5 个 BAL

在下一个第 2 行中，获取前一个 BAL，即 5，然后减去第 2 行中的 1 个 QTY，然后更新第 2 行 BAL = 4，依此类推。

我的Table

Row	QTY	BAL
1	10	5
2	1	0
3	4	0

期望的输出

Row	QTY	BAL
1	10	5
2	1	4
3	4	0

Answer 1

UPDATE MyTable, ( SELECT `Row`, `QTY`,
                         @balance := @balance - QTY AS BAL
                  FROM MyTable
                  CROSS JOIN ( SELECT @balance := QTY + BAL
                               FROM MyTable
                               ORDER BY `Row` LIMIT 1 ) as init
                  ORDER BY `Row` ASC) data_for_update
SET MyTable.BAL = data_for_update.BAL
WHERE MyTable.`Row` = data_for_update.`Row`;

fiddle

UPDATE MyTable
JOIN ( SELECT t1.`Row`, t1.QTY, t3.init_balance - SUM(t2.QTY) BAL
       FROM MyTable t1
       JOIN MyTable t2 ON t1.`Row` >= t2.`Row`
       CROSS JOIN ( SELECT QTY + BAL init_balance
                    FROM MyTable
                    ORDER BY `Row` LIMIT 1 ) t3
       GROUP BY t1.`Row`, t1.QTY, t1.BAL, t3.init_balance) data_for_update 
                ON MyTable.`Row` = data_for_update.`Row`
SET MyTable.BAL = data_for_update.BAL;

fiddle

更新下一行中的值 MYSQL

Update Value in next Row MYSQL

mysql

mariadb

sql-update