update query dintr-un tabel in altul

[durie]

Ma chinui de cateva zile si nu am gasit nici o solutie, am mai postat si nimeni nu mi-a dat un raspuns concludent, nu ma ajutat nici un raspuns, poate ca nu m-am facut destul de inteles...

Am doua tabele register_members si friend

Structura tabelelor sunt:


tabel "register_members"


x-----ID------x-----USERNAME------x-----IMAGINE--------x
x-----1-------x------test1--------x---avatar/bg1.jpg---x
x-----2-------x------test2--------x---avatar/bg1.jpg---x
x-------------x-------------------x--------------------x


tabel "friend"


x-----ID------x-------USERNAME---x-------FNAME-------x-----IMAGINE------x
x-----1-------x--------test1-----x-------TEST2-------x--avatar/bg1.jpg--x
x-----2-------x--------test2-----x-------TEST1-------x--avatar/bg.jpg---x
x-------------x------------------x-------------------x------------------x



$add3 = mysql_query("UPDATE friend f SET f.image = rm.image FROM friend AS f INNER JOIN register_members AS rm ON f.id = rm.id WHERE f.username = '$_SESSION[username]' AND rm.username = '$_SESSION[username]'");
$add4 = mysql_query("UPDATE friends f SET f.image = rm.image FROM friend AS f INNER JOIN register_members AS rm ON f.id = rm.id WHERE f.username = '$_GET[username]' AND rm.username = '$_GET[username]'");


Vreau sa fac update din tabelul "register_members" in tabelul "friend" field-ul "IMAGINE" dar la WHERE sa fie WHERE username=$_SESSION[username]..si nu-mi face update deloc, nu mai stiu cum sa fac, unde am gresit...va rog mult ajutati-ma, spuneti-mi cum sa fac ce anume sa inlocuesc la mysql_query ca sa poata face update dintr-un tabel in altul. Multumesc!

Sper ca de data asta m-am facut destul de inteles.