How to take Cartesian product on logical subsets of rows in SELECT query?

Question

Hi All,
I have the following data in seg_tab table.
Seg_no
Seg_value
1
01
2
001
2
002
3
100040
3
100041
3
100042
3
100043
Expected result, which is produced by joining the logical subsets (by seg_no) in rows. The segments can vary, for simplicity it is 3 but it can grow upto any level.
Codes
01.001.100040
01.001.100041
01.001.100042
01.001.100043
01.002.100040
01.002.100041
01.002.100042
01.002.100043
The SQL statements required to create tables and populate it with the data is given below:
CREATE TABLE seg_tab (seg_no NUMBER, seg_value VARCHAR2(10));
--1st Subset
INSERT INTO seg_tab VALUES (1,'01');
--2nd Subset
INSERT INTO seg_tab VALUES (2,'001');
INSERT INTO seg_tab VALUES (2,'002');
--3rd Subset
INSERT INTO seg_tab VALUES (3,'100040');
INSERT INTO seg_tab VALUES (3,'100041');
INSERT INTO seg_tab VALUES (3,'100042');
INSERT INTO seg_tab VALUES (3,'100043');
Any help on guiding how to write the SQL statement will be highly appreciated.
Many Thanks
Kind Regards,
Bilal

Answer 1

Another way
with
seg_tab as
(select 1 seg_no,'01' seg_value from dual union all
select 2,'001' from dual union all
select 2,'002' from dual union all
select 3,'100040' from dual union all
select 3,'100041' from dual union all
select 3,'100042' from dual union all
select 3,'100043' from dual
concatenator(seg,codes) as
(select seg_no,seg_value
   from seg_tab
  where seg_no = 1
union all
select s.seg_no,c.codes || '.' || s.seg_value
   from concatenator c,
        seg_tab s
  where s.seg_no = c.seg + 1
select codes
  from concatenator
where seg = (select max(seg_no) from seg_tab)
order by codes
CODES
01.001.100040
01.001.100041
01.001.100042
01.001.100043
01.002.100040
01.002.100041
01.002.100042
01.002.100043
Regards
Etbin