$sql = mysql_query("SELECT * FROM
patient_db WHERE
MATCH ( Name, id_number )
AGAINST ('+first_word +second_word +third_word' IN BOOLEAN MODE);");
e se você quiser fazer uma pesquisa exata:
$sql = mysql_query("SELECT *
FROM patient_db
WHERE MATCH ( Name, id_number )
AGAINST ('"exact phrase"' IN BOOLEAN MODE);");