java - 在Java中获取最大值sql

Question

*我没有在其他函数中得到 max 的值。返回值为“0”。我尝试但没有成功:( Image

public int PriceMax(int manhom){
        Connection conn = this.connect();
        int max = 0;
        if(conn != null){
            try {
                java.sql.Statement statement = conn.createStatement();
                String sql = "SELECT AVG(GiaSP) from tbsanpham where manhom = '"+manhom+"'";
                ResultSet rs = statement.executeQuery(sql);
                max = rs.getInt(sql);
            } catch (SQLException ex) {
                Logger.getLogger(CSDL.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
        return max;
    }

求助!!!

int manhom = cbbNhomSanPham.getSelectedIndex();
        CSDL csdl = new CSDL();
        int max = csdl.PriceMax(manhom);
        JOptionPane.showMessageDialog(null, "Nhóm sản phẩm: '"+cbbNhomSanPham.getName()+"' \nPrice max: '"+max+"' ");

Answer 1

您没有按应有的方式使用它。

首先，您使用 AVG 但想要 MAX 因此将其更改为 MAX(GiaSP)。其次，您必须使用 rs.next() 将光标移动到第一行，然后从中获取信息。

java.sql.Statement statement = conn.createStatement();
String sql = "SELECT MAX(GiaSP) from tbsanpham where manhom = '"+manhom+"'";
ResultSet rs = statement.executeQuery(sql);
if (rs.next()) {
    max = rs.getInt(1);
}