create view V (
    B_UTF8,
    B_1251 )
as
select cast ( 'BLOB' as blob sub_type text ) as B_UTF8,
       cast ( 'BLOB' as blob sub_type text character set WIN1251 ) as B_1251
  from RDB$DATABASE
;

create collation PXW_CYRL_CI_AI for WIN1251
   from PXW_CYRL
   CASE INSENSITIVE
   ACCENT INSENSITIVE;

select cast( 'qwerty' as blob sub_type text ) collate PXW_CYRL_CI_AI
  from RDB$DATABASE

Undefined name.
Dynamic SQL Error.
SQL error code = -204.
Data type unknown.
COLLATION PXW_CYRL_CI_AI for CHARACTER SET UTF8 is not defined.

create view V (
    QUERTY)
as
select 'qwerty'
  from RDB$DATABASE
;

select c.RDB$COLLATION_NAME
  from RDB$COLLATIONS c
  join RDB$CHARACTER_SETS s on ( s.RDB$CHARACTER_SET_ID = c.RDB$CHARACTER_SET_ID )
 where s.RDB$CHARACTER_SET_NAME = 'WIN1251'

select count(*)
  from RDB$DATABASE
 where 'UPPER' collate <COLLATE_NAME> = 'UppeR'

create collation PXW_CYRL_CI_AI for WIN1251
   from PXW_CYRL
   CASE INSENSITIVE
   ACCENT INSENSITIVE;

select count(*)
  from RDB$DATABASE
 where 'UPPER' collate PXW_CYRL_CI_AI = 'UppeR'

Use CONNECT or CREATE DATABASE to specify a database
SQL> connect debug user SYSDBA password masterkey;
Database:  debug, User: SYSDBA
SQL> select RDB$COLLATION_NAME,
CON>        RDB$COLLATION_ATTRIBUTES
CON>   from RDB$COLLATIONS
CON>  where RDB$COLLATION_NAME in ( 'UNICODE_CI_AI', 'PXW_CYRL_CI_AI' );

RDB$COLLATION_NAME     RDB$COLLATION_ATTRIBUTES
=====================  ========================
UNICODE_CI_AI                                 7
PXW_CYRL_CI_AI                                7

SQL>

create collation PXW_CYRL_CI for WIN1251
  from PXW_CYRL
  case insensitive;

create collation PXW_CYRL_CI_AI for WIN1251
  from PXW_CYRL
  case insensitive
accent insensitive;

create table T (
    CI     varchar(10) collate PXW_CYRL_CI,
    CI_AI  varchar(10) collate PXW_CYRL_CI_AI
);

insert into T (
    CI,
    CI_AI )
values (
    'zZяЯёЁ',
    'zZяЯёЁ' );
commit;

select count(*)  -- возвращает 0
  from T
 where CI = 'ZZЯЯЁЁ';

select count(*)  -- возвращает 1
  from T
 where CI_AI = 'ZZЯЯЁЁ';