DEPARTMENT_ID_FK | EMAIL_ADDRESS
001              | a@example.com
002              | b@example.com
001              | c@example.com

while($dData = oci_fetch_array($q))
{
     $email = $dData['EMAIL_ADDRESS']; // I know when I echoing this variable, it will be like : a@example.comb@example.comc@example.com
}

DEPARTMENT_ID_FK | EMAIL_ADDRESS
001              | a@example.com, c@example.com
002              | b@example.com