Исходный текст на MS SQL, который нужно переписать на postgres.
/*update a set a.rest_rub = abs(b.ok)
    from #Taccount a    
    join t_account_bal_hst b on a.account_number = b.number and b.date1 <= @odate2 and b.date_next > @odate2
    where a.account_number in (select account_number from #Taccount group by account_number having count(account_number) = 1)
    and account_curr <> '643'
    and abs(b.ok) <> a.rest_rub 
*/

    update v_taccount 
    set v_taccount.rest_rub = abs(d.ok)
    from 
    (select c.* from v_taccount c
     join id.t_account_bal_hst b on c.account_number = b.number 
    and b.date1 <= v_odate2::date and b.date_next > v_odate2::date) d;
    and v_taccount.account_number in 
    (select account_number from v_taccount  group by account_number having count(account_number) = 1)
    and v_taccount.account_curr <> '643'
    and abs(b.ok) <> v_taccount.rest_rub;
*/

join id.t_account_bal_hst

id.t_account_bal_hst

and b.date1 <= v_odate2::date and b.date_next > v_odate2::date) d;

with t as (
select * abs(t.ok) as OK, t1.account_number -- убрать звёздочку, что бы не выбирать лишних данных, вычислить ABS
from v_taccount as t1
join id.t_account_bal_hst as t2 on t1.account_number = t2.number
and t2.date1 <= v_odate2::date and t2.date_next > v_odate2::date
and t1.account_number in
(select account_number from v_taccount group by account_number having count(account_number) = 1)
and t1.account_curr <> '643'
and abs( t2.ok) <> t1.rest_rub)
update v_taccount
set rest_rub = abs(t.ok) -- ABS не нужен, вычислен в cte
from t
where t.account_number = v_taccount.account_number;