php - 插入查询不适用于 MySQL

Question

不知道是查询中写错了，还是逻辑错误。问题出在倒数第二行。

<?php
include "connectdb.php";
$userId = mysql_real_escape_string($_GET["userId"]);

$q1 = mysql_query("SELECT * FROM visitors WHERE userId='userId'");
$num = mysql_num_rows($q1);
if($num==1){
    //user exists, update visits and unique values
    $visits = 0;
    while($row=mysql_fetch_array($q1)){
        $visits = $row["visits"] + 1;
        echo $row["visits"] + 1;
    }
    mysql_query("UPDATE visitors SET visits='$visits',unique='no' WHERE userId='$userId'");
    die();
}
//if there is no current visitor
mysql_query("INSERT INTO visitors(userId,visits,unique) VALUES('$userId','1','yes')");
?>

编辑:数据库中的 userId 和访问次数均设置为 INT。

Answer 1

i think first error in in variable name using  in $ql and second is $num==1 if in visitors table multiple record of thats user then this condition will be wrong ($num==1) so i think replace it with  this ($num>0) 

<?php
include "connectdb.php";
$userId = mysql_real_escape_string($_GET["userId"]);

$q1 = mysql_query("SELECT * FROM visitors WHERE userId='$userId' ");
$num = mysql_num_rows($q1);
if($num>0)
{
    //user exists, update visits and unique values
    $visits = 0;
    while($row=mysql_fetch_array($q1))
    {
        $visits = $row["visits"] + 1;
        echo $row["visits"] + 1;
    }
    mysql_query("UPDATE visitors SET visits='$visits',unique='no' WHERE userId='$userId'");
    die();
}
//if there is no current visitor
mysql_query("INSERT INTO visitors(`userId`,`visits`,`unique`) VALUES ('$userId','1','yes') ");
?>