SELECT
Tw.tw_Id,
Tw.tw_Symbol,
Tw.tw_Nazwa,
Stan = SUM(Tw.Stan),
Rezerwacja = SUM(Tw.Rezerwacja),
Dostepne = SUM(Tw.Dostepne),
cena = MIN(Tw.tc_CenaNetto{0}),
    cena_brutto = MIN(Tw.tc_CenaBrutto{0}),
    EAN = ISNULL(kod.kk_Kod, '')
FROM
vwTowar AS Tw
LEFT JOIN
tw_KodKreskowy AS kod ON kod.kk_IdTowar = Tw.tw_Id
WHERE
(
    st_MagId = {1}
        OR
    st_magId IN ( SELECT mag_id FROM dbo.sl_Magazyn WHERE mag_Symbol IN ({2}) )
OR
    st_MagId IS NULL
)
AND
    Tw.tw_SklepInternet = 1
GROUP BY
Tw.tw_Id, Tw.tw_Symbol, Tw.tw_Nazwa, kod.kk_Kod
ORDER BY Tw.tw_Symbol ASC