Re: cast to domain with default collation issue.

Otherwise, all input expressions must have the same implicit collation
> derivation or the default collation. If any non-default collation is
> present, that is the result of the collation combination. Otherwise, the
> result is the default collation.
>

I think the above quote part can be used to explain the  following
examples.

> CREATE TABLE test1 ( a text COLLATE "de_DE", b text COLLATE "es_ES", c
> text );
> SELECT a < 'foo' FROM test1;

SELECT c < 'foo' FROM test1;

But the *non-default* seems not that correct for me. Like a column if
it does not mention anything, then the default value is null. So
* create table test111( a tex*t) The default collation for column a is
the same as the output of  *show lc_collate*.

so there is no *non-default? *




On Tue, May 24, 2022 at 10:43 AM David G. Johnston <
david.g.johnston@gmail.com> wrote:

> On Monday, May 23, 2022, jian he <jian.universality@gmail.com> wrote:
>
>> CREATE DOMAIN testdomain AS text;
>>
>>  --asume the default collation is as per show LC_COLLATE;
>>
>> – on my pc, it is C.UTF-8.
>>
>> --So the testdomain will be collation "C.UTF-8"
>> ------------
>>
>> => \d collate_test1
>>
>>             Table "test.collate_test1"
>>
>>  Column |  Type   | Collation | Nullable | Default
>>
>> --------+---------+-----------+----------+---------
>>
>>  a      | integer |           |          |
>>
>>  b      | text    | en-x-icu  | not null |
>>
>> -----------------------------------------------
>>
>> My guess is that the following should be the same.
>>
>>
>>
> My reading of the docs say this is consistent with outcome #2.
>
> https://www.postgresql.org/docs/current/collation.html
>
>  David J.
>
>

-- 
 I recommend David Deutsch's <<The Beginning of Infinity>>

  Jian