9.4.2015, 15:43, Glyn Astill kirjoitti:
> From: Scott Marlowe <scott.marlowe@xxxxxxxxx>
> To: Glyn Astill <glynastill@xxxxxxxxxxx>
> Cc: Björn Lundin <b.f.lundin@xxxxxxxxx>;
"pgsql-general@xxxxxxxxxxxxxx" <pgsql-general@xxxxxxxxxxxxxx>
> Sent: Thursday, 9 April 2015, 13:23
> Subject: Re: unexpected (to me) sorting order
>
> On Wed, Apr 8, 2015 at 3:33 AM, Glyn Astill <glynastill@xxxxxxxxxxx>
> wrote:
>
>>
>>> From: Björn Lundin <b.f.lundin@xxxxxxxxx>
>>> To: pgsql-general@xxxxxxxxxxxxxx
>>> Sent: Wednesday, 8 April 2015, 10:09
>>> Subject: unexpected (to me) sorting order
>>>
>>> select * from T_SORT order by NAME ;
>>>
>>> rollback;
>>> id | name
>>> ----+--------------------
>>> 1 | FINISH_110_150_1
>>> 2 | FINISH_110_200_1
>>> 3 | FINISH_1.10_20.0_3
>>> 4 | FINISH_1.10_20.0_4
>>> 5 | FINISH_1.10_30.0_3
>>> 6 | FINISH_1.10_30.0_4
>>> 7 | FINISH_120_150_1
>>> 8 | FINISH_120_200_1
>>> (8 rows)
>>>
>>> why is FINISH_1.10_20.0_3 between
>>> FINISH_110_200_1 and
>>> FINISH_120_150_1
>>> ?
>>>
>>> That is why is '.' between 1 and 2 as in 110/120 ?
>>>
>>>
>>> pg_admin III reports the database is created like
>>> CREATE DATABASE bnl
>>> WITH OWNER = bnl
>>> ENCODING = 'UTF8'
>>> TABLESPACE = pg_default
>>> LC_COLLATE = 'en_US.UTF-8'
>>> LC_CTYPE = 'en_US.UTF-8'
>>> CONNECTION LIMIT = -1;
>>>
>>>
>>
>>
>>
>> The collation of your "bnl" database is utf8, so the
> "." punctuation character is seen as a "variable element"
> and given a lower weighting in the sort to the rest of the characters.
> That's just how the collate algorithm works in UTF8.
>
> utf8 is an encoding method, not a collation. The collation is en_US,
> encoded in utf8. You can use C collation with utf8 encoding just fine.
> So just replace UTF8 with en_US in your sentence and you've got it
> right.
>
Yes, thanks for the correction there, and we're talking about the wider
unicode collate algorithm.
Add some more letters lower/upper and so on. Then compare sorting ex.
ö/z. Or look 0/! order with or without other chars.
We have so many "sorting rules" and standards.
insert into T_SORT values ( 10,'FINISH_Z');
insert into T_SORT values ( 11,'FINISH_a');
insert into T_SORT values ( 12,'FINISH_b');
insert into T_SORT values ( 13,'FINISH_A');
insert into T_SORT values ( 14,'FINISH_B');
insert into T_SORT values ( 15,'FINISH_ä');
insert into T_SORT values ( 16,'FINISH_Ä');
insert into T_SORT values ( 17,'FINISH_+');
insert into T_SORT values ( 18,'FINISH_@');
insert into T_SORT values ( 19,'FINISH_=');
insert into T_SORT values ( 20,'FINISH_]');
insert into T_SORT values ( 21,'FINISH_a0a');
insert into T_SORT values ( 22,'FINISH_a!a');
insert into T_SORT values ( 23,'FINISH_!');
insert into T_SORT values ( 24,'FINISH_012');
insert into T_SORT values ( 25,'FINISH_0aa');
insert into T_SORT values ( 26,'FINISH_!aa');
insert into T_SORT values ( 27,'FINISH_0');
select * from T_SORT order by NAME ; -- use your db LC_COLLATE
-- using COLLATE need that you have installed those locales in
-- your system, PG use those.
select * from T_SORT
ORDER BY name COLLATE "en_US" ;
select * from T_SORT
ORDER BY name COLLATE "fi_FI" ;
select * from T_SORT
ORDER BY name COLLATE "C" ;
select * from T_SORT
ORDER BY name COLLATE "POSIX" ;
select * from T_SORT
ORDER BY name COLLATE "de_DE" ;
Sorting - it's not so easy ... but with COLLATE option you can "fix"
your order if you need / as you want
http://en.wikipedia.org/wiki/ISO_14651
http://en.wikipedia.org/wiki/European_ordering_rules
http://standards.iso.org/ittf/PubliclyAvailableStandards/index.html
- ISO/IEC 14651:2011/Amd 1:2012
https://www.debian.org/doc/manuals/intro-i18n/ - how the library works
http://en.wikipedia.org/wiki/Internationalization_and_localization
...
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare
...
-jukka-
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