问题
I'm quite new to PL/SQL and I need to get the names and count of the distinct characters in a string. E.g. if I have a string str="helloexample", I need to get output of distinct characters in str, i.e. heloxamp.
How can I do this?
回答1:
You can use regular expression as follows:
SET serveroutput ON
DECLARE
str VARCHAR2(20):='helloexample';
str_length NUMBER;
c VARCHAR2(20):=NULL;
d NUMBER;
BEGIN
str_length:=LENGTH(str);
FOR i IN 1..str_length
LOOP
IF regexp_instr(c,SUBSTR(str,i,1))>0 THEN
NULL;
ELSE
c:=c||SUBSTR(str,i,1);
END IF;
END LOOP;
dbms_output.put_line(c);
END;
the answer would be:
heloxamp
回答2:
if WM_CONCAT isnt working for you, you can use this trick:
select rtrim(xmlagg(xmlelement(e, str)).extract('//text()'), ',') as output
from (select substr(str, level, 1) str, level l,
row_number() over (partition by substr(str, level, 1)
order by level) rn
from (select 'helloexample' str from dual) d
connect by level <= length(str)
order by level)
where rn = 1;
SQL> select rtrim(xmlagg(xmlelement(e, str)).extract('//text()'), ',') as output
2 from (select substr(str, rownum, 1) str, level l,
3 row_number() over (partition by substr(str, rownum, 1) order by level) rn
4 from (select 'helloexample' str from dual) d
5 connect by level <= length(str)
6 order by level)
7 where rn = 1;
OUTPUT
--------------------------------------------------------------------------------
heloxamp
来源：https://stackoverflow.com/questions/14748730/how-to-find-count-and-names-of-distinct-characters-in-string-in-pl-sql