You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AND gh_artikel_kundennummern.akn_art_nr = '7405'' at line 1SELECT akn_vka FROM gh_artikel_kundennummern WHERE gh_artikel_kundennummern.akn_kd_nr =  AND gh_artikel_kundennummern.akn_art_nr = '7405'