with t1 (id, n, date1, fld2, fld3) as
(
              select 1, 0, to_date('10.10.2020', 'DD.MM.YYYY'), 12, 34 from dual
    union all select 2, 0, to_date('11.10.2020', 'DD.MM.YYYY'), 56, 78 from dual
)
, dop1 (n, date1, str, fld2, fld3) as
(
    select 1, to_date('10.10.2020', 'DD.MM.YYYY'), 'Доп строка 1', 21, 43 from dual
)
, dop2 (n, date1, str, fld2, fld3) as
(
    select 2, to_date('10.10.2020', 'DD.MM.YYYY'), 'Доп строка 2', 2, 3 from dual
    union all
    select 2, to_date('11.10.2020', 'DD.MM.YYYY'), 'Доп строка 2', 7, 8 from dual
)
, dop3 (n, date1, str, fld2, fld3) as
(
    select 3, to_date('10.10.2020', 'DD.MM.YYYY'), 'Доп строка 3', 1, 4 from dual
    union all
    select 3, to_date('11.10.2020', 'DD.MM.YYYY'), 'Доп строка 3', 222, 5 from dual
)
, t (id, n, date1, str, fld2, fld3) as
(
select t1.id, n, t1.date1, to_char(t1.date1, 'DD.MM.YYYY'), t1.fld2, t1.fld3 from t1
union all
select t1.id, dop1.n, t1.date1, dop1.str, dop1.fld2, dop1.fld3
  from t1 join dop1 on t1.date1 = dop1.date1
union all
select t1.id, dop2.n, t1.date1, dop2.str, dop2.fld2, dop2.fld3
  from t1 join dop2 on t1.date1 = dop2.date1
union all
select t1.id, dop3.n, t1.date1, dop3.str, dop3.fld2, dop3.fld3
  from t1 join dop3 on t1.date1 = dop3.date1
)
select str
     , case when date1 = to_date('11.10.2020', 'DD.MM.YYYY') and n = 3 
            then t.fld2/2 else t.fld2 end as fld2
     , case when date1 = to_date('10.10.2020', 'DD.MM.YYYY') and t.fld2 = 21
            then (select 65 from dual) else t.fld3 end as fld3
  from t
order by date1, n

with t1 (id, n, date1, fld2, fld3) as
(
              select 1, 0, to_date('10.10.2020', 'DD.MM.YYYY'), 12, 34 from dual
    union all select 2, 0, to_date('11.10.2020', 'DD.MM.YYYY'), 56, 78 from dual
)
, dop (n, str) as
(
              select 1, 'Доп строка 1' from dual
    union all select 2, 'Доп строка 2' from dual
    union all select 3, 'Доп строка 3' from dual
    
)
, t (id, n, date1, str, fld2, fld3) as
(
select t1.id, n, t1.date1, to_char(t1.date1, 'DD.MM.YYYY'), t1.fld2, t1.fld3 from t1
union all
select t1.id, dop.n, t1.date1, dop.str, t1.fld2 + 11, t1.fld3 + 11 from t1, dop
)
select str
     , case when date1 = to_date('11.10.2020', 'DD.MM.YYYY') and n = 1 
            then t.fld2 * (lead(t.fld3 + 1) over (partition by date1 order by n))
            else t.fld2 
            end as calculated_fld2
     , case when date1 = to_date('10.10.2020', 'DD.MM.YYYY') and n = 3 
            then lag(t.fld3, 3) over (partition by date1 order by n) *
                 (select fld2 from t1 where id = 1) 
            else t.fld3 
            end as calculated_fld3
  from t
order by date1, n