Re: cast to domain with default collation issue.

"David G. Johnston" <david.g.johnston@xxxxxxxxx> · Tue, 24 May 2022 23:38:24 -0700

Please don’t top-post.

On Tuesday, May 24, 2022, jian he <jian.universality@xxxxxxxxx> wrote:

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 text) The default collation for column a is the same as the output of  show lc_collate. 
so there is no non-default? 

I’m not following the point you are trying to make.  table111.a contributes the default collation for any _expression_ needing a collation implicitly resolved.

David J.