select
s.specification_id
s.specification
c.contract_id
c.contract
u.usr_id
u.login
z.contragent_id
z.contragent
z.external_code
from specification s
left outer join contract c on (s.contract_id=c.contract_id)
left outer join usr u on (c.contragent_id=u.contragent_id)
left outer join contragent z on (u.contragent_id=z.contragent_id)
where u.usr_id=
order by specification_id desc;