Question

我想知道,删除这一声明是否实际上删除了某些内容。下面的法典总是执行。是否删除了部分内容。这样做的恰当方式是什么?

public Deleter(String pname, String pword) {

        try {
            PreparedStatement createPlayer = conn.prepareStatement("DELETE FROM players WHERE P_Name= "+ pname +"  AND P_Word= " + pword + " ");
            createPlayer.execute();

            if(createPlayer.execute()==true){

            JOptionPane.showMessageDialog(null, "Player successfully deleted!");

            }else{

                 JOptionPane.showMessageDialog(null, "Player does not exist!", "notdeleted", JOptionPane.ERROR_MESSAGE);
            }

        } catch (Exception e) {
        }
    }

Answer 1

你实际上两次执行删除声明,因为你两次打电话.execute()。在大多数情况下,如果你几乎立即第二次掌握,你就不太可能有可以通过说明删除的数据。

相反,使用executeUpdate(meth。退还给您的行文数目

int rowsAffected = createPlayer.executeUpdate();

if(rowsAffected > 0) {
   JOptionPane.showMessageDialog(null, "Player successfully deleted!");
}
else{
    JOptionPane.showMessageDialog(null, "Player does not exist!", "notdeleted", JOptionPane.ERROR_MESSAGE);
}

Answer 2

Use executeUpdate. It returns an int parameter telling you the number of rows affected. Also, be careful, in your code you are executing the statement twice.

Answer 3

您应取代Player.execute(Player.execute);对于一名创造者来说,当他们返回时,就意味着受到影响的浏览次数。你们需要做的是,如果是零,就不必这样做。

Answer 4

使用最新()来计算增长额。

还有一些重大项目需要更正在您的法典中:

You are not using PreparedStatement correctly. Use parameters instead.
Don t swallow exceptions. At the least print a stack trace but showing a message to the user would be nice.
You are running the statement twice. Just do it once in your if statement.

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