插入查询不适用于MySQL

Question

I don't know if wrote something wrong in the query, or if it's a logic error. The problem is on the second to last line.

<?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')");
?>

EDIT: userId and visits are both set to INT in the database.

Answer 1

1.

Change:

$q1 = mysql_query("SELECT * FROM visitors WHERE userId='userId'");

to:

$q1 = mysql_query("SELECT * FROM visitors WHERE userId=$userId");

2.

Delete the single quotes around $userId in your SQL queries (since it's an INT). It should be like this:

mysql_query("UPDATE visitors SET visits='$visits',`unique`='no' WHERE userId=$userId");

and:

mysql_query("INSERT INTO visitors(userId,visits,`unique`) VALUES($userId,'1','yes')");

Answer 2

You should add error handling to your sql queries, but the problem (after the correction indicated by @DanielLisik) is the use of a reserved word : unique .

Change your query to:

mysql_query("INSERT INTO visitors(userId,visits,`unique`) VALUES('$userId','1','yes')");

You should also consider changing to PDO or mysqli as the mysql_* functions are deprecated.

Answer 3

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') ");
?>