我认为这就是您要寻找的。NEW_BAL是QTY从余额中减去的s 的总和：

SELECT   master_table.ORDERNO,
         master_table.ITEM,
         SUM(master_table.QTY),
         stock_bal.BAL_QTY,
         (stock_bal.BAL_QTY - SUM(master_table.QTY)) AS NEW_BAL
FROM     master_table INNER JOIN
         stock_bal ON master_bal.ITEM = stock_bal.ITEM
GROUP BY master_table.ORDERNO,
         master_table.ITEM

如果要使用新余额更新项目余额，请使用以下命令：

UPDATE stock_bal
SET    BAL_QTY = BAL_QTY - (SELECT   SUM(QTY)
                            FROM     master_table
                            GROUP BY master_table.ORDERNO,
                                     master_table.ITEM)

假设您向后发布减法；它从天平中按顺序减去数量，这在不了解表格的情况下最有意义。如果我错了，只需交换这两个即可更改它：

(SUM(master_table.QTY) - stock_bal.BAL_QTY) AS NEW_BAL