declare
  type t_queen is varray(8) of number;
  queen t_queen := t_queen(1, 2, 3, 4, 5, 6, 7, 8);
  l_num number := 0;
  -- 顯示“八皇后”
  procedure show(queen t_queen) is
  begin
    l_num := l_num + 1;
    dbms_output.put_line(rpad('---- NO. ' || l_num || ' ', 16, '-'));
    -- 從第1行顯示到第8行
    for r in 1 .. 8 loop
      -- 當前行，從第1列顯示到第8列
      for c in 1 .. 8 loop
        -- “皇后”用“Q”表示，空位用“.”表示
        dbms_output.put(case when queen(r) = c then 'Q' else '.'
                        end || ' ');
      end loop;
      dbms_output.put_line(null);
    end loop;
  end;
  -- 沖突檢測。檢測第row行與第1行至第row-1行是否沖突。
  -- 不沖突，返回true；沖突返回false
  function is_ok(queen t_queen, row number) return boolean is
    t number;
  begin
    for r in 1 .. row - 1 loop
      if queen(r) = queen(row) then
        -- 第row行與第r行的皇后在同一列上，沖突
        return false;
      end if;
      t := queen(r) - queen(row);
      if t = r - row or t = row - r then
        -- 第row行與第r行的皇后在同一斜線上，沖突
        return false;
      end if;
    end loop;
    return true;
  end;
  -- 遞歸查找所有排列
  procedure find(queen in out t_queen, row number) is
  begin
    for col in 1 .. 8 loop
      -- 每一行列的位置從第1列到第8列檢測
      queen(row) := col;
      if is_ok(queen, row) then
        if row = 8 then
          -- 已經查找到第8行，查找結束，顯示結果
          show(queen);
          return;
        end if;
        find(queen, row + 1); -- 尚未查找到第8行，第歸查找一下行
      end if;
    end loop;
  end;
begin
  find(queen, 1); -- 從第1行開始查找
end;

with sou as (
     select level n,1 k from dual connect by  level<=8
),
     ntt(n,k) as (
     select sou.n ,sou.k  from sou where k=1
     union all
     select ntt.n*10+a.n
            ,ntt.k+1 
     from ntt,sou a
     where not exists(select 1
                      from  (select level b1 from dual connect by level<=7) t
                      where t.b1<=ntt.k and (
                             a.n=to_number(substr(to_char(ntt.n),b1,1)) or
                             a.n=to_number(substr(to_char(ntt.n),b1,1))+(ntt.k+1-t.b1) or
                             a.n=to_number(substr(to_char(ntt.n),b1,1))-(ntt.k+1-t.b1)
                             )
                     ) and ntt.k<=7
     )
select n from ntt where ntt.k=8  ;