搜索现有数据，如果是php，则加倍

我正在处理一个网页，我希望有一个可能的删除按钮，其工作方式如下：

 - you introduce a country ISO code which you want to delete
 - click the button
 - if the country has players participating (competitor table, ISO_country_code column) then prints the message that this cannot happen
 - if not, deletes the country from country table

我尝试了以下方法，但我不知道如何创建第二个if的条件，以实现适当的工作

$connect=mysqli_connect("localhost","root","","mydatabase");
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }
 else 
 {
    $result=mysqli_query($connect,"SELECT COUNT(*) FROM competitor
        WHERE ISO_country_code='".$_POST['countrycode']."')")
    if ($result>0)
    {
        echo 'The following country is involved with players, so it can not be deleted!</br></br>';
    }
    else (mysqli_query($connect,"DELETE FROM country WHERE     ISO_country_code='".$_POST['countrycode']."'"));
    {
        echo 'The following country was deleted: '.$_POST["countrycode"]."</br>";
    }
}       

---

您有一些语法错误+可能没有得到要查找的行数

$connect=mysqli_connect("localhost","root","","mydatabase");
if (mysqli_connect_errno())
  {
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
  }
 else 
 {
    $result=mysqli_query($connect,"SELECT * FROM competitor
        WHERE ISO_country_code='".$_POST['countrycode']."'");
     $rows = mysql_num_rows($result);
    if ($rows>0)
    {
        echo 'The following country is involved with players, so it can not be deleted!</br></br>';
    }
    else {
      mysqli_query($connect,"DELETE FROM country WHERE ISO_country_code='".$_POST['countrycode']."'");
        echo 'The following country was deleted: '.$_POST["countrycode"]."</br>";
  }
}  

使用面向对象的方法时，$结果不包含整数，它返回true或false或对象

如果要检查查询返回的结果数量，必须用函数替换$result

您应该了解如何防止SQL注入

首先，您必须使用以下内容创建查询的准备语句：

$stmt = mysqli_prepare($connect,"SELECT * FROM competitor WHERE ISO_country_code=?");

然后将参数绑定到语句s代表字符串：

mysqli_stmt_bind_param($stmt,"s",$_POST['countrycode']);

并执行您的声明：

mysqli_stmt_execute($stmt);

然后，您可以使用获得结果，例如。

试试这个

if(mysql_num_rows($result) > 0)
    {
    echo "cannot delete";
    }
    else if(mysql_num_rows($result) == 0)
    {
     //write the query for deletion
    echo "deleted";
    }

---

请注意1'；落桌国家在这篇文章中会非常戏剧化，你这是什么意思？小心你的代码中的SQL注入，你可能想开始使用准备好的语句……最好的SQL注入保护是有的。这是一个很好的观点，但如果不应该的话，仍然会进入第二阶段。@rafanadal你是什么意思？