select id from doc_list
where id >= (select min(id)-0.5 from doc_list) + rand()*( (select max(id)+0.5 from doc_list) - (select min(id)-0.5 from doc_list))
order by id;

execute block returns(id int) as
  declare id_rnd int;
begin
  id_rnd = (select min(id)-0.5 from doc_list) 
             + rand() * 
             ( (select max(id)+0.5 from doc_list) - (select min(id)-0.5 from doc_list) );

  select h.id from doc_list h where h.id >= :id_rnd order by id into id;
  suspend;
end

    select id from doc_list
    where id >= (select min(id)-0.5 from doc_list) 
                    + (select distinct rand() r from rdb$database) * 
                       ( (select max(id)+0.5 from doc_list) - (select min(id)-0.5 from doc_list))
    rows 1;

execute block returns(id int, cnt int, cnt_avg double precision, deviation_percent double precision) as
declare r double precision;
declare variable id_rnd int;
declare variable n int = 10000;
begin
  delete from t;
  while (n>0) do begin
    insert into t -- log: t(id int);
    select id from doc_list
    where id >= (select min(id)-0.5 from doc_list) 
      + (select distinct rand() r from rdb$database) 
      * ( (select max(id)+0.5 from doc_list) - (select min(id)-0.5 from doc_list))
    rows 1;
    n=n-1;
  end

  for select id,count(*), avg(count(*))over(), 100.00 * (count(*)-avg(count(*))over()) / avg(count(*))over()
  from t group by id
  into id, cnt, cnt_avg, deviation_percent
  do suspend;
end

recreate table doc_list(id int);
insert into doc_list values(0);
insert into doc_list values(1);
insert into doc_list values(2);
insert into doc_list values(3);
insert into doc_list values(4);
insert into doc_list values(5);
insert into doc_list values(6);
insert into doc_list values(7);
insert into doc_list values(8);
insert into doc_list values(9);

recreate table t(id int);
commit;
set term ^;
execute block returns(id int, cnt int, cnt_avg double precision, deviation_percent double precision) as
declare r double precision;
declare variable id_rnd int;
declare variable n int = 100000;
begin
  delete from t;
  while (n>0) do begin
    insert into t
     select id from doc_list
    where id >= (select min(id)-1 from doc_list) 
                + (select distinct rand() r from rdb$database) 
                * ( (select max(id)+1 from doc_list) - (select min(id)-1 from doc_list))
    rows 1; 
    n=n-1;
  end

  for select id,count(*), avg(count(*))over(), 100.00 * (count(*)-avg(count(*))over()) / avg(count(*))over()
  from t group by id
  into id, cnt, cnt_avg, deviation_percent
  do suspend;
end^
set term ;^
commit;