php - 选择列的总和 - 几个变量

Question

这是我目前的选择声明：

$sql17="SELECT SUM(TotalProfit)-('$sum14','$sum13') AS TotalProfit FROM jwtdriversbank2";

我可以毫无问题地减去一个这样的变量：

$sql17="SELECT SUM(TotalProfit)-'$sum14' AS TotalProfit FROM jwtdriversbank2";

但是我希望能够减去几个变量，我该怎么做？？？？

Answer 1

像这样？

$sql17="SELECT SUM(TotalProfit)-'$sum14'-'$sum13' AS TotalProfit FROM jwtdriversbank2";

通过像这样直接注入变量来构造 SQL 查询时要小心，尽可能使用准备好的语句。

Answer 2

$sum_to_substract = $sum14+$sum13; //add all vars that you want to substract
$sql17="SELECT SUM(TotalProfit)-'$sum_to_substract' AS TotalProfit FROM jwtdriversbank2";