with src_data(reg, nd, np, kp, stp) as (
 values
  (6, 129241, cast('1988-10-03' as date), cast('1997-05-31' as date), '1-1'),

  (6, 129241, cast('1997-07-01' as date), cast('1998-02-08' as date), '1-1'),

  (6, 129241, cast('1998-02-17' as date), cast('1998-06-03' as date), '1-1'),
  (6, 129241, cast('1998-06-04' as date), cast('1998-10-01' as date), '1-1'),

  (6, 129241, cast('1998-10-07' as date), cast('1999-04-27' as date), '1-1'),
  (6, 129241, cast('1999-04-28' as date), cast('2003-08-31' as date), '1-1'),
  (6, 129241, cast('2003-09-01' as date), cast('2003-09-21' as date), '1-1'),
  (6, 129241, cast('2003-09-22' as date), cast('2003-12-31' as date), '1-1'),
  (6, 129241, cast('2004-01-01' as date), cast('2004-02-01' as date), '1-1'),
  (6, 129241, cast('2004-02-02' as date), cast('2010-11-19' as date), '1-1'),
  (6, 129241, cast('2010-11-20' as date), cast('2011-03-31' as date), '1-1')
),
get_prev_kp(reg, nd, np, kp, stp, prev_kp) as (
 select reg, nd, np, kp, stp, 
        LAG(kp) OVER (PARTITION BY reg, nd, stp order by np) as prev_kp -- значение kp от "предыдущей строки"
 from src_data
),
gen_seq_inc(reg, nd, np, kp, stp, seq_inc) as (
 select reg, nd, np, kp, stp,
        case when prev_kp + 1 day = np then 0  -- та же последовательность
		     else 1                            -- новый интервал
	    end as seq_inc -- increment номера последовательности
 from get_prev_kp
),
gen_seq_num(reg, nd, np, kp, stp, seq_num) as (
 select reg, nd, np, kp, stp,
        sum(seq_inc) over(PARTITION BY reg, nd, stp 
		                  order by nd ROWS UNBOUNDED PRECEDING
				     ) as seq_num -- номер последовательности (считаем как сумму инкрементов по всем предыдущим строкам)
 from gen_seq_inc
)
select reg, nd, min(np), max(kp), stp
from gen_seq_num
group by reg, nd, stp, seq_num;

with get_prev_d2(sn, d1, d2, stp, prev_d2) as (
 select sn, d1, d2, stp, 
        LAG(d2) OVER (PARTITION BY sn, stp order by d1) as prev_d2 -- значение d2 от "предыдущей строки"
 from t11_dopl
),
gen_seq_inc(sn, d1, d2, stp, seq_inc) as (
 select sn, d1, d2, stp,
        case when prev_d2 + 1 day = d1 then 0  -- та же последовательность
             else 1                            -- новый интервал
        end as seq_inc -- increment номера последовательности
 from get_prev_d2
),
gen_seq_num(sn, d1, d2, stp, seq_num) as (
 select sn, d1, d2, stp,
        sum(seq_inc) over(PARTITION BY sn, stp 
                          order by d1 ROWS UNBOUNDED PRECEDING
                     ) as seq_num -- номер последовательности (считаем как сумму инкрементов по всем предыдущим строкам)
 from gen_seq_inc
)
select sn, min(d1), max(d2), stp
from gen_seq_num
group by sn, stp, seq_num;