$wpdb not working for me.

Simple question but no one seems to find an answer to it.. why.. idk..

This following question is based off of “$wpdb”
How to take $current_user->logged_in
and check if it is in the database under “guestbook (table)” and “names (column)…

Here’s my code…

$query = "SELECT * FROM myguestbook"; 

// execute query
$result = mysql_query($query) or die ("Error in query: $query. ".mysql_error()); 

// see if any rows were returned
 if (mysql_num_rows($result) > 0) {
    // yes
    // print them one after another
    echo "<table cellpadding=10 border=1>";
    while($row = mysql_fetch_row($result)) {
        echo "<tr>";
        echo "<td>"."<center>".$row[0]."</center>"."</td>";
        echo "<td>" . $row."</td>";
        echo "<td>".$row."</td>";
        echo "</tr>";
    } 

}
else {
    // none
    // print status message
    echo "No rows found!";
}

So.. Im able to get the data.. but here’s where im stuck… I want to take the data from the database and put it in a IF statement.
Example
<?php if ($row(0) = $current_user->logged_in) {//do something...} ?>

I can’t seem to have it check the whole Table.. it only checks to see if the first entry is the name.. Any ideas?