declare @max_stop int
DECLARE @block_num INT
set @max_stop = 0
set @block_num = 1
BEGIN
with test as(
select 1 as id, 1 as start, 2 as stop
UNION all select 2 as id, 1 as start, 3 as stop
UNION all select 3 as id, 2 as start, 3 as stop
UNION all select 4 as id, 10 as start, 14 as stop
UNION all select 5 as id, 11 as start, 13 as stop
UNION all select 6 as id, 14 as start, 15 as stop
),
b as (select *,lag(stop) over(order by id)  as prev_value_stop
from test
), 
c as (
select id, start, case when prev_value_stop < start then stop else prev_value_stop end prev_value_stop
from b)
select *,lag(prev_value_stop) over(order by id)  as prev
from c 

end

WITH 
test AS (
	SELECT 1 AS id, 1 AS start, 2 AS stop
	UNION ALL
	SELECT 2 AS id, 1 AS start, 3 AS stop
	UNION ALL
	SELECT 3 AS id, 2 AS start, 3 AS stop
	UNION ALL
	SELECT 4 AS id, 10 AS start, 14 AS stop
	UNION ALL
	SELECT 5 AS id, 11 AS start, 13 AS stop
	UNION ALL
	SELECT 6 AS id, 14 AS start, 15 AS stop
),
    a as (
    select *, lag(stop) over(order by id) stop2
    from test),

    b as(
    select id,start, 
      		case 
      			when stop2 is null then stop 
      			when start > stop2 then stop else stop2 
      		end stop3
    from a
    ),

    c as(
    select *,  case when lag(stop3) over(order by id) >= start then 0 else 1 end block_num_check
    from b)
    
select id, start, stop3, sum(block_num_check) over(order by id) block_num
from c