有趣的小小SQL

题目：给一个整数，如何得到一个有规律的字符串。比如：2得到12；3得到123；4要得到1234；5得到12345，而6得到123456；当数值大于7时，大于7的数都为7。比如8得到12345677； 10得到1234567777等，整数值最大为24

下面是我的方法：

create or replace procedure SP_TEST(str_in in integer) is

output varchar2(200);

begin
  
   select case when str_in > 7 then rpad('1234567',str_in,'7') 
   else substr('1234567',0,str_in) end into output 
          from dual;
   
   DBMS_OUTPUT.put_line(output);
end SP_TEST;

测试结果：

 

以下为网友的代码：

VAR N NUMBER;
EXEC :N:=5;
SELECT LPAD(RPAD('1234567',30,'7'),:N) FROM DUAL;

测试结果：

 

分析：

我使用了Oracle中的case when 逻辑判断 以及rpad、substr函数来实现。而网友见使用了lpad和rpad来实现。

下面是lpad，rpad、substr，的用法：

http://www.techonthenet.com/oracle/functions/lpad.php

Oracle/PLSQL: Lpad Function

---

 

In Oracle/PLSQL, the lpad function pads the left-side of a string with a specific set of characters (whenstring1 is not null).

The syntax for the lpad function is:

lpad( string1, padded_length, [ pad_string ] )

string1 is the string to pad characters to (the left-hand side).

padded_length is the number of characters to return. If the padded_length is smaller than the original string, the lpad function will truncate the string to the size ofpadded_length.

pad_string is optional. This is the string that will be padded to the left-hand side ofstring1. If this parameter is omitted, the lpad function will pad spaces to the left-side ofstring1.

Applies To:

• Oracle 8i, Oracle 9i, Oracle 10g, Oracle 11g

For Example:

lpad('tech', 7);	would return '   tech'
lpad('tech', 2);	would return 'te'
lpad('tech', 8, '0');	would return '0000tech'
lpad('tech on the net', 15, 'z');	would return 'tech on the net'
lpad('tech on the net', 16, 'z');	would return 'ztech on the net'

 

Oracle/PLSQL: Rpad Function

---

 

In Oracle/PLSQL, the rpad function pads the right-side of a string with a specific set of characters (whenstring1 is not null).

The syntax for the rpad function is:

rpad( string1, padded_length, [ pad_string ] )

string1 is the string to pad characters to (the right-hand side).

padded_length is the number of characters to return. If the padded_length is smaller than the original string, the rpad function will truncate the string to the size ofpadded_length.

pad_string is optional. This is the string that will be padded to the right-hand side ofstring1. If this parameter is omitted, the rpad function will pad spaces to the right-side ofstring1.

Applies To:

• Oracle 8i, Oracle 9i, Oracle 10g, Oracle 11g

For Example:

rpad('tech', 7);	would return 'tech   '
rpad('tech', 2);	would return 'te'
rpad('tech', 8, '0');	would return 'tech0000'
rpad('tech on the net', 15, 'z');	would return 'tech on the net'
rpad('tech on the net', 16, 'z');	would return 'tech on the netz'