Question

I have problem with sorting elements by varchar containing Polish characters like ą, Ą.

For example, we have following names:

Aaaa
BBcvx
Ąccc
Ddde
ądcc

Following query:

select * from something order by lower(name);

Returns result as this:

Aaaa
BBcvx
Ddde
ądcc
Ąccc

As you can see, polish characters are ignored and put at the end. It should be:

Aaaa
ądcc
Ąccc
BBcvx
Ddde

What might be the problem? Database encoding? Mine is:

SELECT * FROM NLS_DATABASE_PARAMETERS WHERE PARAMETER = 'NLS_CHARACTERSET';

Result:
EE8MSWIN1250

Can this be fixed without changing database encoding?

Answer 1

You need to look into the NLS_SORT parameter, specifically linguistic sorting. You can use this parameter to specify what language you’d like to sort by. I suspect in your case it would be POLISH.

Something like this

select *
  from something
 order by nls_lower(name, 'NLS_SORT' = 'POLISH')

NLS_LOWER() returns a lower case character in the same manner as an ordinary LOWER().

You could also do this at a session level, which would change the default sort parameter for the duration of the session.

alter session set nls_sort = POLISH;

If you wanted to always use this sort; this is done the database level when the database is created.