如何减去总库存中的库存？

Question

我正在研究医院项目。我的问题是：我有两张桌子（1）。股票和（2）。的信息。

库存表包含药品总库存。

详细信息表包含totalstockquantity - soldstock数量。

我试过这个代码：

$result=mysql_query(
"SELECT ((stock.quantity)-details.quantity) AS sub,
 stock.id AS id,
 stock.name AS name,
 stock.type AS type,
 stock.batch_no AS batch,
 stock.quantity AS quantity,
 stock.exp AS exp
 FROM stock
 INNER JOIN details on stock.name=details.medicine ");
?>

但它会给出同一个id的多个结果。

Answer 1

SELECT stock.quantity - (select sum(details.quantity) from details where stock.name=details.medicine) AS sub,
 stock.id AS id,
 stock.name AS name,
 stock.type AS type,
 stock.batch_no AS batch,
 stock.quantity AS quantity,
 stock.exp AS exp
 FROM stock