如何在Oracle中从字符串中获取唯一字符?

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问题描述

How to get the unique characters from a string in Oracle?

假设我有一列包含数据

CCCXXXCCCCCCCCCCCCCCCCXXCCCCCCCCCCCCCCCCCCCCCCC

，我想返回'CX'作为唯一字符列表.

and I want to return 'CX' as the list of unique characters.

同样:aaaabbbccccdddaaa ==> abcd，HelloO ==> HeloO

likewise: aaaabbbccccdddaaa ==> abcd , HelloO ==> HeloO

顺序很重要，我希望它们与第一次出现在字符串中的顺序相同.

Order is important, I want them to be in the same order as they first appear in the string.

有没有不用存储过程的方法吗?

Is there any way to do it without using stored procedure?

添加更多示例

推荐答案

SELECT SUBSTR(REGEXP_SUBSTR('CCCCXXXCCCCCCCCCCCCCCCCXXCCCCCCCCCCCCCCCCCCCCCCC', '^(.)\1*.'), -2, 2) RESULT
FROM DUAL;

它返回CX

这是另一种解决方案:

Select Replace (Wm_Concat (C), ',', '')
From
  (Select Substr ('CCCXCCCXXXCCCCCCCCCCCCCCCCXXCCCCCCCCCCCCCCCC', Rownum, 1) C,
    Min (Rownum) Rn
  From Dual
    Connect By Rownum <= Length ( 'CCCXCCCXXXCCCCCCCCCCCCCCCCXXCCCCCCCCCCCCCCCC')
  Group By Substr ( 'CCCXCCCXXXCCCCCCCCCCCCCCCCXXCCCCCCCCCCCCCCCC', Rownum, 1)
  Order By Rn
  ) X;

它按出现的顺序返回所有唯一字符.顺便说一句，是的，这看起来太可怕了

It returns all the unique chars in order of their occurence. Btw, yes, it looks horrible

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cx