Question

我正在尝试使用供应商数据库创建一个swing应用程序。以下Howewer SQL查询由于某种原因返回null。如果在数据库中找不到增值税号，则此查询应创建供应商帐户。这个错误背后的原因是什么？

我的代码：

public void actionPerformed(ActionEvent e) {
    try {
        String vName = vendorField.getText();
        String adress = adressField.getText();
        String country = (String) countryField.getSelectedItem();
        String vat = vatField.getText();
        String pTerms = ptermsField.getText();
        String iban = ibanField.getText();
        String myDriver = "com.mysql.jdbc.Driver";
        String myUrl = "jdbc:mysql://localhost:3306/masterdata_db?autoReconnect=true&useSSL=false";

        Connection conn = DriverManager.getConnection(myUrl, "root", "");

        Statement st = conn.createStatement();
        ResultSet resultSet;

        String check = "SELECT * FROM vendorcreation WHERE VAT = '"+vatField.getText()+"'";      
        resultSet = st.executeQuery(check);

        boolean status = true;

        if(resultSet.next()!=status){
            String sql1 = "INSERT INTO vendorcreation"
                    + "(VendorName, Adress, VAT, PaymentTerms, IBAN, Country) VALUES"
                    + "(?,?,?,?,?,?)";
            PreparedStatement pSt2=conn.prepareStatement(sql1);
            pSt2.setString(1, vName);
            pSt2.setString(2, adress);    
            pSt2.setString(3, vat);
            pSt2.setString(4, pTerms);    
            pSt2.setString(5, iban);  
            pSt2.setString(6, country);   

            pSt2.executeUpdate(sql1);  
            JOptionPane.showMessageDialog(frame, "VENDOR ACCOUNT CREATED!");
        } else {
            JOptionPane.showMessageDialog(frame, "VENDOR ALREADY EXISTS!", "Inane error",JOptionPane.ERROR_MESSAGE);
        }
    } catch (Exception e1) {
        System.err.println("AN ERROR OCCURRED! PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR.");
        System.err.println(e1.getMessage());
    }
}

Answer 1

在select语句中将“=”更改为“LIKE”，

String check = "SELECT * FROM vendorcreation WHERE VAT LIKE '"+vatField.getText()+"'";

下面的SQL查询返回null - JAVA gui

1 个答案: