mySQL Hatası:
SELECT DISTINCT fu2.UrunID FROM vtx_fatura_urunleri fu1 INNER JOIN vtx_fatura_urunleri fu2 ON fu1.FaturaID = fu2.FaturaID INNER JOIN vtx_basvurular u ON u.id = fu2.UrunID WHERE fu1.UrunID = 2534 AND fu2.UrunID != 2534 AND u.Yayin=1 AND u.Tamam=1 AND u.Durum=1 AND u.ProjeTipi=1 AND ((b.SiteID='5' or b.SiteID='6' or b.SiteID='8' or b.SiteID='1')u.SiteID='5' or u.SiteID='6' or u.SiteID='8' or u.SiteID='1') and u.Stok>0 GROUP BY fu2.UrunID ORDER BY RAND() LIMIT 20;

You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'u.SiteID='5' or u.SiteID='6' or u.SiteID='8' or u.SiteID='1')
  and u.Stok>0
...' at line 11