错误：加入MySql，PHP

I have two tables in mysql one is quote and the fields are quote_id, status, created and submit_by. in submit_by field i am saving username of the employee and in employee table the fields are firs_name, last_name, username, password. I want to show in a php table the employee first name instead of username of the employee.

full quote table stucture

full employee table sructure

this is the code i am using but not getting any result

$sql = "SELECT q.quote_id, q.client_name, q.status, e.first_name 
        FROM `quote` AS q 
        LEFT JOIN `employee` AS e ON q.submit_by = e.username";

Use this one

$sql = "SELECT * , employee.first_name FROM quote 
LEFT JOIN employee ON quote.submit_by = employee.username ORDER BY quote.client_name";
$result = $dbLink->query($sql);

You can use below Query to get the result.

SELECT q.`quote_id`, q.`client_name`, q.`status`, e.`first_name` FROM `quote` q , `employee` e WHERE q.`submit_by` = e.`username`;

try this:

 SELECT quote.quote_id, quote.client_name, quote.status, employee.first_name FROM quote 
    LEFT JOIN employee ON quote.submit_by = employee.username ORDER BY quote.client_name;