PHP MySql query inside another query is returning null

Question

I just need to create a simple php page that can query one table(ad_data), and compare two columns against rows in another table(time_clock_data), and return the value of the column 'Login Name' in time_clock_data. However, when i run the page it pulls everything from ad_data fine, but the time_clock_data 'Login Name' returns null.

Here is my code:

<?php

    mysql_connect("localhost", "root", "") or die (mysql_error ());
    $conn = new mysqli("localhost", "root", "", "uh_time_clock");

    mysql_select_db("uh_time_clock") or die(mysql_error());

    function queryAd(){

        $adQuery = mysql_query("SELECT * FROM ad_data ORDER BY 'First Name' DESC");
        while($ad = mysql_fetch_array($adQuery)) {

            $adFirstName = $ad['First Name'];
            $adLastName = $ad['Last Name'];
            $adLoginName = $ad['Login Name'];

            echo "<li>" . $adLoginName . "</li>";

            mysql_select_db("uh_time_clock") or die(mysql_error());

            $tcQuery = "SELECT * FROM time_clock_data WHERE 'First Name' = '$adFirstName' and 'Last Name' = '$adLastName'";
            $tc = mysql_fetch_assoc( mysql_query($tcQuery) );

            $tcLoginName = $tc['Login Name'];

            echo "<li>" . $tcLoginName . "</li>";

        }
    }

    queryAd();

    mysql_close();

    ?>