Postgres natural order by

Question

I have a sorting issue in postgres in a column with values such as version. Version is character varying, with values such as the following (un-ordered).

1.2
1.3
1.10.1
1.9

How do I sort in natural order such that when I issue SELECT version FROM TABLE_A ORDER BY version DESC it will give me

1.10.1
1.9
1.3
1.2

instead of

1.9
1.3
1.2
1.10.1

Answer 1

Postgres allow you to sort by arrays -- which is essentially what the version number represents. Hence, you can use this syntax:

order by string_to_array(version, '.')::int[] desc

Here is a full example:

select *
from (values ('1'), ('2.1'), ('1.2.3'), ('1.10.6'), ('1.9.4')) v(version)
order by string_to_array(version, '.')::int[] desc;

And even a demonstration.

Answer 2

One way: (works if version may have maximum 3 parts)

with t(col) as(
    select '1.9' union all
    select '2' union all
    select '1.2' union all
    select '1.10.1'  
)
select * from t
order by 
case when split_part(col, '.', 1) = '' then 0 else split_part(col, '.', 1)::int end desc, 
case when split_part(col, '.', 2) = '' then 0 else split_part(col, '.', 2)::int end desc, 
case when split_part(col, '.', 3) = '' then 0 else split_part(col, '.', 3)::int end desc