代码示例：

CREATE OR REPLACE FUNCTION order_string (str IN VARCHAR2) RETURN VARCHAR2 IS ordered_str VARCHAR2(32767) := ''; BEGIN FOR i IN 1..LENGTH(str) LOOP ordered_str := ordered_str || SUBSTR(str, i, 1) || ','; END LOOP;

ordered_str := RTRIM(ordered_str, ',');
SELECT LISTAGG(val, '') WITHIN GROUP (ORDER BY val) INTO ordered_str
FROM (SELECT DISTINCT REGEXP_SUBSTR(ordered_str,'[^,]+',1,level) AS val FROM DUAL
      CONNECT BY REGEXP_SUBSTR(ordered_str,'[^,]+',1,level) IS NOT NULL);

RETURN ordered_str;

END;

使用示例：

SELECT order_string('abcdecbadf') FROM DUAL;

结果为：aabbccdddef