如何获得另一列的项目值=值的列的总和？

Question

我的代码：

string hweight = "Hunters"; 
string hsql = "SELECT SUM(Weight), Product From Opened WHERE Product =" + hweight; 

OleDbCommand hcmd = new OleDbCommand(hsql,conn); 
txtHunters.Text = hcmd.ExecuteScalar().ToString(); 

然后我收到以下错误：

You tried to execute a query that does not include the specified expression 'Product' as part of an aggregate function.

Answer 1

你的SQL应该是：

SELECT SUM(Weight), Product From Opened WHERE Product =" + hweight + " GROUP BY Product" 

当你使用你的东西应该将它们分组聚合函数！在你的情况下，产品领域！

Answer 2

您尽量选择字段/列，并在同一时间使用聚合函数，即只有当你选定字段/列提供group by条款以及工作原理：

string hsql = "SELECT SUM(Weight), Product FROM Opened WHERE Product ='" + hweight + "' GROUP BY Product"; 

Answer 3

试试这个，

string hweight = "Hunters"; 
string hsql = "SELECT SUM(Weight), Product From Opened WHERE Product =" + hweight + " GROUP BY Product"; 
OleDbCommand hcmd = new OleDbCommand(hsql,conn); 
txtHunters.Text = hcmd.ExecuteScalar().ToString();