text: -- Adapted: 13-Jul-2020 (Bob Heckel--https://connor-mcdonald.com/2020/07/10/uniquely-random-or-randomly-unique/)
  create table t ( pk number);
  
  create sequence seq start with 1000000 maxvalue 9999999 cycle;
  
  set timing on
  
  begin
    for i in 1 .. 1000 loop
      insert into t values ( to_number(trunc(dbms_random.value(1000,9999))|| to_char(systimestamp,'FFSS')|| seq.nextval) );
    end loop;
  end;
  
  -- This identifier is “always” unique because in order to encounter a violation
  -- we would need to generate the same sequence number as it cycles around, along
  -- with the same random value from our random number generator, and chance upon
  -- both of those repeated values at the same fraction of a second within a one minute.
  select pk from t where rownum <= 20;
  