Question

如何从mysql数据库中减去输入？让我们说我正在做一个帐单和库存系统。因此，当用户在jtextfield上输入数量时，它会从表中减去。将附加GUI。

现在，我写了这个方法

    public boolean updateBill(Bill bi) {
    boolean success = false;
    dbController db = new dbController();
    PreparedStatement ps;

    try {

        myConn = DriverManager.getConnection("jdbc:mysql://localhost:3306/ooadp?useSSL=false", "root", "pass"); 

        Statement myStatement = myConn.createStatement();

        String sql = "UPDATE medicalproduct SET  quantity =  quantity - ? WHERE productID = ?, productName = ?, dosage = ?, price = ?, status = ?" ;

        myStatement.executeUpdate(sql);



        myConn.close();

    } catch (Exception e) {
        e.printStackTrace();
    }

    return success;

}

但后来我不知道在actionPerform上写什么以及如何将我的jtextfield链接到sql查询。

This is how my gui looks like

Answer 1

你的sql语句无论如何都是无效的...但如果是对的，你想要做的就是从jTextField中指定的值中减去数据库中的字段

//For example quantity -= txtfieldValue;

如果你想要的话。您可以查询字段的值，进行减法，然后最后更新字段。以下是仅更新数量的示例：

public void updateQuantity(String txtFieldValue,String id) throws ClassNotFoundException, SQLException{
        Class.forName("com.mysql.jdbc.Driver");
        System.out.println("Driver loaded!!!");
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/ooadp?useSSL=false", "root", "pass");
        System.out.println("Connection  created!!!");

        PreparedStatement pState;

        String sqlRawP1 ="select quantity from medicalproduct  where productID=?";//I guess medicalproduct is your table name
        pState = conn.prepareStatement(sqlRawP1);
        pState.setString(1, id);
        ResultSet rSetQuantity = pState.executeQuery();

        int countQuantity = 0;
        while(rSetQuantity.next()){
            countQuantity = rSetQuantity.getInt(1);//Am assumming that quantity is an integer
        }

        int value = Interger.parseInt(txtFieldValue);

        countQuantity-= value;

        String sqlRawP2 = "update medicalproduct set quantity=? where productID=?";
        pState = conn.prepareStatement(sqlRawP2);
        pState.setInt(1,countQuantity);
        pState.setString(2, id);

        pState.executeUpdate();

}

希望它能很好地工作。如果有轻微的错误，请原谅我，因为我自己没有测试过。

如何从jtextfield减去mysql数据库的输入？

1 个答案: