Oracle sql to case conversion for every adjacent characters in a string - sql

Question

With a condition like no two adjacent characters ( from a to z) should be in same case;
I need to change helloworld to HeLlOwOrLd , and used a query like :
SELECT listagg(jumping_char,'') WITHIN GROUP(ORDER BY rn) jumped_word
FROM
(SELECT rn,
CASE
WHEN mod(rn, 2) = 1
THEN upper(split_word)
ELSE lower(split_word)
END jumping_char
FROM
(SELECT regexp_substr('helloworld','.',LEVEL)split_word,
ROWNUM rn
FROM dual
CONNECT BY LEVEL <= LENGTH('helloworld')
)
);
Now I got a string like hello2world should becomes HeLlO2wOrLd.
Any simple ,different queries are appreciated and thanks in advance.

Answer 1

If I understand you correctly, you want to "skip" over non-characters in the input. You can achieve that by using regexp_count() with an offset of rn (instead of simply using rn) in your old solution:
SELECT listagg(jumping_char,'') WITHIN GROUP(ORDER BY rn) jumped_word
FROM
(SELECT rn,
CASE
when mod (regexp_count('hello2world', '[a-zA-Z]', rn), 2) = 1
THEN upper(split_word)
ELSE lower(split_word)
END jumping_char
FROM
(SELECT regexp_substr('hello2world','.',LEVEL)split_word,
ROWNUM rn
FROM dual
CONNECT BY LEVEL <= LENGTH('hello2world')
)
);
UPDATE:
Here's an alternative solution using the MODEL clause, just for completeness' sake:
with t as
(select 'hello2world' txt from dual)
select listagg(case
when mod(v2.char_cnt, 2) = 1
then upper(v2.txt)
else lower(v2.txt)
end,
'') within group(order by v2.rn)
from (
select
v1.txt,
rownum as rn,
sum(case
when regexp_like(txt, '[a-zA-Z]')
then 1
else 0
end) over (partition by 1 order by rownum) as char_cnt
from (
SELECT TXT
FROM T
MODEL
RETURN UPDATED ROWS
PARTITION BY(ROWNUM RN)
DIMENSION BY (0 POSITION)
MEASURES (TXT ,length(txt) NB_MOT)
RULES
(TXT[FOR POSITION FROM 1 TO NB_MOT[0] INCREMENT 1] =
substr(txt[0], CV(POSITION), 1) )
) v1
) v2