Oracle 18c

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create function my_random_emplID(p_seed in number default null)
return number is
begin
  if p_seed is not null then
    dbms_random.seed(utl_raw.cast_to_raw(p_seed));
  end if;
  return dbms_random.value;
end;
/
SELECT
  CONCAT('USER',CAST(1.0 + FLOOR(250000 * my_random_emplID(1452)) as varchar(6))) as mask_id
FROM
  dual;


MASK_ID


USER213750


SELECT
  CONCAT('USER',CAST(1.0 + FLOOR(250000 * my_random_emplID(1452)) as varchar(6))) as mask_id
FROM
  dual;


MASK_ID


USER213750