SQL select two same column on same table but with different ORDER - sql

Question

Trainee here.
I need to create a list last names from the same table.
say we have a table named "sample", this table only consists of:
What I want to do here is both last name column will be selected but have different order, the first column would be ascending and the second column would be descending like the photo below

Answer 1

Here's one option: it splits first and last name into two subqueries which use row_number analytic function. It is then used to join rows.
Lines #1 - 6 represent your sample data. Query you really need begins at line #7.
SQL> with test (last_name, first_name) as
2 (select 'L1one' , 'F1one' from dual union all
3 select 'L2two' , 'F2two' from dual union all
4 select 'L3three', 'F3hthree' from dual union all
5 select 'L4four' , 'F4four' from dual
6 ),
7 ln as
8 (select last_name,
9 row_Number() over (order by last_name) rn
10 from test
11 ),
12 fn as
13 (select first_name,
14 row_number() over (order by first_name desc) rn
15 from test
16 )
17 select l.last_name, f.first_name
18 from ln l join fn f on f.rn = l.rn
19 order by l.last_name
20 /
LAST_NA FIRST_NA
------- --------
L1one F4four
L2two F3hthree
L3three F2two
L4four F1one
SQL>
[EDIT: both last names? I thought it was a typo]
If that's so, self-join is a better option:
SQL> with test (last_name, first_name) as
2 (select 'L1one' , 'F1one' from dual union all
3 select 'L2two' , 'F2two' from dual union all
4 select 'L3three', 'F3hthree' from dual union all
5 select 'L4four' , 'F4four' from dual
6 ),
7 temp as
8 (select last_name,
9 row_number() over (order by last_name asc) rna,
10 row_number() over (order by last_name desc) rnd
11 from test
12 )
13 select a.last_name, d.last_name
14 from temp a join temp d on a.rna = d.rnd
15 order by a.last_name;
LAST_NA LAST_NA
------- -------
L1one L4four
L2two L3three
L3three L2two
L4four L1one
SQL>

Answer 2

Here is one way to do it. In a single subquery, assign the ordinal number (rn) based on ascending order, but also keep track of the total row count. Then follow with a join.
with
test (last_name, first_name) as (
select 'L1one' , 'F1one' from dual union all
select 'L2two' , 'F2two' from dual union all
select 'L3three', 'F3hthree' from dual union all
select 'L4four' , 'F4four' from dual
)
, prep (last_name, rn, ct) as (
select last_name, row_number() over (order by last_name), count(*) over ()
from test
)
select a.last_name as last_name_asc, b.last_name as last_name_desc
from prep a inner join prep b on a.rn + b.rn = a.ct + 1
;
LAST_NAME_ASC LAST_NAME_DESC
-------------- --------------
L1one L4four
L2two L3three
L3three L2two
L4four L1one