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[英]How can I retrieve a column description from MS ACCESS database using Java
[英]How do I get Sum of a column in Ms Access database using Java?
我想获取一列总和的值并将其显示在文本字段中。
我使用了这段代码,但它不起作用。
public static String invoice() throws SQLException{
Connection con = connect();
String query="SELECT SUM(costM) AS totalsum from Meals";
Statement s =con.createStatement();
s.execute(query);
ResultSet rs=s.getResultSet();
String result =rs.getString("totalsum");
return result;
}
//Method to apply when button clicked
public void message() throws SQLException{
textinv.setText(db.invoice());
}
请参阅此问题的答案。
import java.sql.*;
class TestJava{
public static void main(String args[]){
try{
Class.forName("com.mysql.jdbc.Driver");
Connection con=DriverManager.getConnection(
"jdbc:mysql://localhost:3306/shopping_cart","root","root");
String query = "select sum(meal_cost) as totalSum from customers";
Statement stmt=con.createStatement();
stmt.executeQuery(query);
ResultSet rs=stmt.getResultSet();
while(rs.next())
System.out.println(rs.getString(1));
con.close();
}
catch(Exception e){ System.out.println(e);}
}
}
您面临的问题是由于 cursor 未移动到指定行。 next() function 用于此。
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