UPDATE I
SET
    i.C_FENNTARTOID = f.ID
    ,SERIAL = i.SERIAL + 1
    ,MODIFIER = 0
    ,LASTCHANGED = GETDATE()
FROM
dbo.T_INTEZMENY AS i
INNER JOIN DBO.T_FENNTARTO AS f ON f.TOROLT = 'F' AND i.C_FENNTARTOAZONOSITO = f.C_AZONOSITO
WHERE i.TOROLT = 'F' AND i.C_ISARCHIV = 'F'