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Counting something in SQL


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I have table called private_messages, one of the columns is owner_id, that is equal to account id who message is for. I wrote a code to count all lines that have owner_id equal to my id.


function getidbyName($int) 
$query = "SELECT * FROM users WHERE username='$int'";
$res = mysql_query($query);
$arr = mysql_fetch_row($res);

return $arr[0];


function countMessages($name) {
$id = getidbyName($name);

$query = "SELECT * FROM private_messages WHERE owner_id = '$id'";
$num_rows = mysql_num_rows($query);
return $num_rows;


my error message is


Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in C:\xampp\htdocs\we3\pages\message_center.php on line 18


it used to work then i was trying just to count row's

function countTable($int) {
$result = mysql_query("SELECT * FROM $int");
$num_rows = mysql_num_rows($result);

return $num_rows;


I'm messed up, and can't find the problem myself, if anyone know please helm me :)

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