SELECT manufNeg.manufCode, m.mnf_name
FROM manufacturer as m,  
(
select byr_neg.byrcodeNeg as buyerUser, byr_neg.mnfCodeNeg as manufCode
                                                     FROM user as u, 
                                                                  (
                                                                      select n.ngt_code , n.ngt_buyer_usr_code as byrcodeNeg, n.ngt_procur_usr_code, n.ngt_mnf_code as mnfCodeNeg
                                                                         FROM negotiation as n
                                                                         WHERE n.ngt_procur_usr_code='cv'
                                                                         )
                                                                           as byr_neg
                                                                 WHERE
                                                              u.usr_email=byr_neg.byrcodeNeg
) as manufNeg
WHERE m.mnf_code=manufNeg.manufCode