java - 执行executeQuery时结果集始终为空

Question

我目前正在编写一个简单的 Java 应用程序，它从 XLS 文件中读取信息，然后将其输入数据库中。由于该 XLS 确实有重复的记录，因此我做了一个简单的检查，检查 XLS 文件中的条目是否已存在于数据库中。这是我的代码:

public static void addResult(ArrayList<ArrayList<String>> listResults)
{
    try
    {
        openDatabase();
        stmt = c.createStatement();

        for (int i = 0; i < listResults.size(); i++)
        {
            PreparedStatement stm = c.prepareStatement("SELECT player_name FROM results WHERE player_name=?;");
            stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
            System.out.println(stm);
            ResultSet rs = stm.executeQuery();

            if (rs.getRow() <= 0)
            {
                String typeOfPlay = new String();

                if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Simple"))
                {
                    typeOfPlay = "single";
                }
                else if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Double"))
                {
                    typeOfPlay = "double";
                }

                stm = c.prepareStatement("INSERT INTO results (player_name, school_id, " +  typeOfPlay + ", tournament_id) "
                        + "VALUES(?,?,?,?);");

                stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
                stm.setString(2, listResults.get(i).get(ReadResultsFile.SCHOOL_ID));
                stm.setInt(3, Integer.parseInt(listResults.get(i).get(ReadResultsFile.SCORE)));
                stm.setString(4, "1");
                stm.executeUpdate();
            }
            else
            {
                String typeOfPlay = new String();

                if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Simple"))
                {
                    typeOfPlay = "single";
                }
                else if (listResults.get(i).get(ReadResultsFile.TYPE).equals("Double"))
                {
                    typeOfPlay = "double";
                }

                stm = c.prepareStatement("UPDATE results SET " + typeOfPlay + "=? WHERE player_name=?;");

                stm.setString(1, typeOfPlay);
                stm.setString(2, listResults.get(i).get(ReadResultsFile.SCORE));
                stm.setString(1, listResults.get(i).get(ReadResultsFile.NAME));
                System.out.println(stm);
                stm.executeUpdate();
            }
        }

        closeDatabase();
    }
    catch (Exception e)
    {
        System.err.println(e.getClass().getName() + ": " + e.getMessage());
        System.exit(0);
    }
}

出现的问题是 rs.getRow() 函数始终返回 -1。我尝试直接在数据库工具中运行 SELECT 查询，如果已经存在类似的条目，则查询将返回player_name 列。不幸的是，它在 Java 中也做了同样的事情。

我现在不确定该怎么做。

感谢您的任何提示!

Answer 1

getRow 将无法按照 javadocs 工作

Retrieves the current row number. The first row is number 1, the second number 2, and so on.

和

A ResultSet cursor is initially positioned before the first row; the first call to the method next makes the first row the current row

通常使用

while (rs.next ()) {....