繪製圖案使用Oracle SQL

Question

我想畫兩個圖案和我堅持用不同的問題：

1）

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* 
NULL 

我已經寫了下面的查詢來獲取這樣的：

select CASE WHEN (r2-r1)!=0 THEN 
     rpad('*',r2-r1,'*') END 
from (select rownum r1 
      ,(max(level) over()) as r2 
    from dual 
    connect by level<=20); 

我面臨的問題（如果你看圖）是空的即將結束。我無法想出辦法擺脫這一點。

2）我想繪製與每個星星之間的空間相同的模式。卡在這裏太..

所有的幫助將是非常可觀的。

Answer 1

SQL> select rpad('*', level, '*') as c from dual connect by level <= 20 order by 
    length(c) desc; 

C 
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20 rows selected. 

SQL> select rpad('*', 2*level-1, ' *') as c from dual connect by level <= 20 order by 
    length(c) desc; 

C 
-------------------------------------------------- 
* * * * * * * * * * * * * * * * * * * * 
* * * * * * * * * * * * * * * * * * * 
* * * * * * * * * * * * * * * * * * 
* * * * * * * * * * * * * * * * * 
* * * * * * * * * * * * * * * * 
* * * * * * * * * * * * * * * 
* * * * * * * * * * * * * * 
* * * * * * * * * * * * * 
* * * * * * * * * * * * 
* * * * * * * * * * * 
* * * * * * * * * * 
* * * * * * * * * 
* * * * * * * * 
* * * * * * * 
* * * * * * 
* * * * * 
* * * * 
* * * 
* * 
* 

20 rows selected. 

Answer 2

就過濾掉的行，其中最大等於ROWNUM：

SELECT 
    rpad('*', r2 - r1, '*') c1, 
    rpad('* ', (r2 - r1) * 2, '* ') c2 
FROM 
    (SELECT ROWNUM r1, max(LEVEL) OVER() AS r2 FROM dual CONNECT BY LEVEL <= 20) 
WHERE 
    r1 < r2