Does sql analytic function help to determine continuity in occurences

Question

We need to solve this problem in a sql statement.
imagine a table test with two columns
create table test (id char(1), begin number, end number);
and these values
insert into test('a',1, 2);
insert into test('a',2,3);
insert into test('a',3,4);
insert into test('a',7,10);
insert into test('a',10,15);
insert into test('b',5,9);
insert into test('b',9,21);
insert into test('c',1,5);
our goal is to determine continuity in number sequence between begin and end attributes for a same id and determine min and max number from these contuinity chains.
The result may be
a, 1, 4
a, 7, 15
b, 5, 21
c, 1, 5
We test some analytic functions like lag, lead, row_number, min, max, partition by, etc to search a way to identify row set that represent a continuity but we didn't find a way to identify (mark) them so we can use min and max functions to extract extreme values.
Any idea is really welcome !

Answer 1

Here is our implementation in a real context for example:
insert into requesterstage(requesterstage_i, requester_i, t_requesterstage_i, datefrom, dateto )
With ListToAdd as
(Select distinct support.requester_i,
support.datefrom,
support.dateto
from support
where support.datefrom < to_date('01.01.2006', 'dd.mm.yyyy')
and support.t_relief_i = t_relief_ipar.fgetflextypologyclassitem_i(t_relief_ipar.fismedicalexpenses)
and not exists
(select null
from requesterstage
where requesterstage.requester_i = support.requester_i
and support.datefrom < nvl(requesterstage.dateto, support.datefrom + 1)
and nvl(support.dateto, requesterstage.datefrom + 1) > requesterstage.datefrom)
ListToAddAnalyzed_1 as
(select requester_i,
datefrom,
dateto,
decode(datefrom,lag(dateto) over (partition by requester_i order by datefrom),0,1) data_set_start
from ListToAdd),
ListToAddAnalyzed_2 as
(select requester_i,
datefrom,
dateto,
data_set_start,
sum(data_set_start) over(order by requester_i, datefrom ) data_set_id
from ListToAddAnalyzed_1)
select requesterstage_iseq.nextval,
requester_i,
t_requesterstage_ipar.fgetflextypologyclassitem_i(t_requesterstage_ipar.fisbefore2006),
datefrom,
decode(sign(nvl(dateto, to_date('01.01.2006', 'dd.mm.yyyy')) -to_date('01.01.2006', 'dd.mm.yyyy')), 0, to_date('01.01.2006', 'dd.mm.yyyy'), -1, dateto, 1, to_date('01.01.2006', 'dd.mm.yyyy'))
from ( select requester_i
, min(datefrom) datefrom
, max(dateto) dateto
From ListToAddAnalyzed_2
group by requester_i, data_set_id
);