MySQL 计数功能无法正常工作

Question

$req_user = trim($_GET['user']);
    mysql_connect("$host", "$username", "$password")or die("cannot connect");
    mysql_select_db("$db_name")or die("cannot select DB");
$get_data = "SELECT * FROM `users` WHERE uname = '$req_user'";
$result = mysql_query($get_data) OR die(mysql_error());
$rows = mysql_fetch_assoc($result);
$email = $rows['email'];
$gravatar = md5(strtolower(trim("$email")));
$user_likes = mysql_query("SELECT COUNT(*) FROM likes WHERE username = '$email'");

我正在尝试计算数据库中喜欢的所有行以及用户名字段中当前用户的电子邮件。
（这是一个从 userinfo.php?user=xxx 等链接获取信息的循环。）
当我 echo $user_likes 时没有输出。

代码有什么问题？
http://www.tutorialspoint.com/mysql/mysql-count-function.htm

Answer 1

假设 $gravatar = md5(strtolower(trim("$email"))); 与此处的问题无关且不需要，您还可以使用一个数据库查询来获取数数：

$req_user = trim($_GET['user']);
mysql_connect("$host", "$username", "$password") or die("cannot connect");
mysql_select_db("$db_name") or die("cannot select DB");
$get_count_query = 
    "SELECT COUNT(*)
     FROM likes 
     WHERE username = 
           ( SELECT email
             FROM users 
             WHERE uname = '$req_user'
           )
    ";
$result = mysql_query($get_count_query) or die(mysql_error());
$row = mysql_fetch_row($result);
$user_likes = $row[0];

Answer 2

你没有获取它...

这样做：

$result = mysql_query("SELECT COUNT(*) FROM likes WHERE username = '$email'");

$user_likes = mysql_fetch_row($result);

Answer 3

首先，您需要正确比较电子邮件（不区分大小写）：

"... WHERE UPPER(username) = '" . strtoupper($email) . "'"

然后 $user_likes 是一个资源变量，它不会直接给您计数。

您需要先获取它：

$row = mysql_fetch_row($user_likes);
echo 'Count: ' . $row[0]; 

Answer 4

你应该这样做：

$req_user = trim($_GET['user']);
mysql_connect("$host", "$username", "$password") or die("cannot connect");
mysql_select_db("$db_name") or die("cannot select DB");
$get_data = "SELECT * FROM `users` WHERE uname = '$req_user'";
$result = mysql_query($get_data) or die(mysql_error());
if ($rows = mysql_fetch_assoc($result)) {
    $email = $rows['email'];
    $gravatar = md5(strtolower(trim("$email")));
    $get_data = "SELECT COUNT(*) FROM likes WHERE username = '$email'";
    $user_likes = mysql_query($get_data) or die(mysql_error());
    if ($row = mysql_fetch_row($user_likes)) {
       $nbr = 1*$row[0]; 
    } else {
       // it could never happen ;-)
       $nbr = 0;
    }
} else {
    // no match with this user!
    $nbr = 0;
}
echo "This user likes $nbr times !";