random no. generation in MySQL database table??how to fix this?

Here is the code I used:

$inserttimesheet = mysql_query("
    INSERT INTO `employeetimesheets`(employee,date_start,date_end,status)
    VALUES (".$emp_Id = $_SESSION['employees'].",'$start','$end','Pending')"
);

while ($timesheet = mysql_fetch_array($restimesheet_id)) {
    $timesheet_ID = $timesheet['id'];
}