Question

ResultSet rs = stm.executeQuery("SELECT count(*) FROM `hs` WHERE `username` ='"+c.playerName+"' LIMIT 1");
int rows = 0;

try
{
    rs.last();
    rows = rs.getRow();
    rs.beforeFirst();
} 
catch(Exception ex)
{
    ex.printStackTrace();
    return false;
}

if(rows > 0)
{
    query("UPDATE `hs` SET `overall_lvl` = '"+overallLVL+"',`overall_xp` = '"+overallXP+"',`attack_lvl` = '"+c.playerLevel[0]+"',`attack_xp` = '"+c.playerXP[0]+"',`defence_lvl` = '"+c.playerLevel[1]+"',`defence_xp` = '"+c.playerXP[1]+"',`strength_lvl` = '"+c.playerLevel[2]+"',`strength_xp` = '"+c.playerXP[2]+"',`ranged_lvl` = '"+c.playerLevel[3]+"',`ranged_xp` = '"+c.playerXP[3]+"',`prayer_lvl` = '"+c.playerLevel[4]+"',`prayer_xp` = '"+c.playerXP[4]+"',`magic_lvl` = '"+c.playerLevel[5]+"',`magic_xp` = '"+c.playerXP[5]+"',`cooking_lvl` = '"+c.playerLevel[6]+"',`cooking_xp` = '"+c.playerXP[6]+"',`woodcutting_lvl` = '"+c.playerLevel[7]+"',`woodcutting_xp` = '"+c.playerXP[7]+"',`fletching_lvl` = '"+c.playerLevel[8]+"',`fletching_xp` = '"+c.playerXP[8]+"',`fishing_lvl` = '"+c.playerLevel[9]+"',`fishing_xp` = '"+c.playerXP[9]+"',`firemaking_lvl` = '"+c.playerLevel[10]+"',`firemaking_xp` = '"+c.playerXP[10]+"',`crafting_lvl` = '"+c.playerLevel[11]+"',`crafting_xp` = '"+c.playerXP[11]+"',`smithing_lvl` = '"+c.playerLevel[12]+"',`smithing_xp` = '"+c.playerXP[12]+"',`mining_lvl` = '"+c.playerLevel[13]+"',`mining_xp` = '"+c.playerXP[13]+"',`herblore_lvl` = '"+c.playerLevel[14]+"',`herblore_xp` = '"+c.playerXP[14]+"',`agility_lvl` = '"+c.playerLevel[15]+"',`agility_xp` = '"+c.playerXP[15]+"',`thieving_lvl` = '"+c.playerLevel[16]+"',`thieving_xp` = '"+c.playerXP[16]+"',`slayer_lvl` = '"+c.playerLevel[17]+"',`slayer_xp` = '"+c.playerXP[17]+"',`farming_lvl` = '"+c.playerLevel[18]+"',`farming_xp` = '"+c.playerXP[18]+"',`runecrafting_lvl` = '"+c.playerLevel[19]+"',`runecrafting_xp` = '"+c.playerXP[19]+"',WHERE `username` = '"+c.playerName+"'");
}
else
{
    query("INSERT INTO `hs` SET `username` = '"+c.playerName+"', `overall_lvl` = '"+overallLVL+"',`overall_xp` = '"+overallXP+"',`attack_lvl` = '"+c.playerLevel[0]+"',`attack_xp` = '"+c.playerXP[0]+"',`defence_lvl` = '"+c.playerLevel[1]+"',`defence_xp` = '"+c.playerXP[1]+"',`strength_lvl` = '"+c.playerLevel[2]+"',`strength_xp` = '"+c.playerXP[2]+"',`ranged_lvl` = '"+c.playerLevel[3]+"',`ranged_xp` = '"+c.playerXP[3]+"',`prayer_lvl` = '"+c.playerLevel[4]+"',`prayer_xp` = '"+c.playerXP[4]+"',`magic_lvl` = '"+c.playerLevel[5]+"',`magic_xp` = '"+c.playerXP[5]+"',`cooking_lvl` = '"+c.playerLevel[6]+"',`cooking_xp` = '"+c.playerXP[6]+"',`woodcutting_lvl` = '"+c.playerLevel[7]+"',`woodcutting_xp` = '"+c.playerXP[7]+"',`fletching_lvl` = '"+c.playerLevel[8]+"',`fletching_xp` = '"+c.playerXP[8]+"',`fishing_lvl` = '"+c.playerLevel[9]+"',`fishing_xp` = '"+c.playerXP[9]+"',`firemaking_lvl` = '"+c.playerLevel[10]+"',`firemaking_xp` = '"+c.playerXP[10]+"',`crafting_lvl` = '"+c.playerLevel[11]+"',`crafting_xp` = '"+c.playerXP[11]+"',`smithing_lvl` = '"+c.playerLevel[12]+"',`smithing_xp` = '"+c.playerXP[12]+"',`mining_lvl` = '"+c.playerLevel[13]+"',`mining_xp` = '"+c.playerXP[13]+"',`herblore_lvl` = '"+c.playerLevel[14]+"',`herblore_xp` = '"+c.playerXP[14]+"',`agility_lvl` = '"+c.playerLevel[15]+"',`agility_xp` = '"+c.playerXP[15]+"',`thieving_lvl` = '"+c.playerLevel[16]+"',`thieving_xp` = '"+c.playerXP[16]+"',`slayer_lvl` = '"+c.playerLevel[17]+"',`slayer_xp` = '"+c.playerXP[17]+"',`farming_lvl` = '"+c.playerLevel[18]+"',`farming_xp` = '"+c.playerXP[18]+"',`runecrafting_lvl` = '"+c.playerLevel[19]+"',`runecrafting_xp` = '"+c.playerXP[19]+"'");

}

当我运行它时，它只会执行插入，在第二次运行时它不会再次执行。我相信这些行没有正确地变成int。我该怎么做才能正确设置？

Answer 1

您的代码应为：

int rows; // No need to initialize
try (PreparedStatement stmt = conn.prepareStatement("SELECT count(*)" +
                                                     " FROM `hs`" +
                                                    " WHERE `username` = ?")) { // No need for LIMIT 1
    stmt.setString(1, c.playerName); // This prevents syntax errors and SQL Injection issues
    try (ResultSet rs = stmt.executeQuery()) {
        rs.next(); // SELECT count(*) always returns exactly 1 row
        rows = rs.getInt(1); // Get value of first column
    }
}

请（！）也使用PreparedStatement作为INSERT和UPDATE语句。

Answer 2

不确定为什么你在那里last()和getRow() - 获得一个而且只有你的计数（*）的结果的“默认”方式是这样的：

int rows = 0;
try {
  //Check if there is a row - the if you could leave out in this case.
  if(rs.next()) {
    //Get the int as position 1 in the result - that's your count(*)
    rows = rs.getInt(1);
  }

请同时考虑关闭您的Statement和ResultSet。否则，您将创建资源泄漏。

此外，您应该检查PreparedStatement并使用它以防止代码中出现SQL注入。

Answer 3

选择计数查询总是返回1行。

您需要获取计数的值并测试该值是否为＆gt; 0或不。

正确的代码应类似于以下内容：

long rows = 0;
try {
   if (rs.next()) {
       rows = rs.getLong(1);
   }
   if (rows > 0) {
       // Query for update
   } else {
       // Query for insert
   }
   ....

其他提示：请勿使用Statement。使用PreparedStament，它解决了与sql注入相关的问题，并且从程序员的角度来看更容易阅读

Answer 4

我建议将查询更改为

SELECT count(*) cnt FROM

然后使用

rs.getInt("cnt"); // do something

在SQL中将SQL计数设置为变量

4 个答案: