Count of each characters in given string - oracle

Question

I require the count of each character in a string.
Example:
SELECT ('aabcccdee') from dual;
Result:
a(1),b(2), c(3), d(1),e(2).
Thanks in advance.

Answer 1

You can use a hierarchical query to split your string into it individual characters; this is using a CTE just to supply your example value:
with t (value) as (
select 'aabcccdee' from dual
)
select substr(value, level, 1) as a_char
from t
connect by level <= length(value);
Then you can use aggregation to count how may times each appears:
with t (value) as (
select 'aabcccdee' from dual
)
select a_char, count(*) a_count
from (
select substr(value, level, 1) as a_char
from t
connect by level <= length(value)
)
group by a_char
order by a_char;
A_CH A_COUNT
---- ----------
a 2
b 1
c 3
d 1
e 2
And you can use listagg() (if you're on 11g or above) to aggregate those characters and counts into a single string if that's what you really want:
with t (value) as (
select 'aabcccdee' from dual
)
select listagg(a_char || '(' || count(*) || ')', ',') within group (order by a_char)
from (
select substr(value, level, 1) as a_char
from t
connect by level <= length(value)
)
group by a_char;
LISTAGG(A_CHAR||'('||COUNT(*)||')',',')WITHINGROUP(ORDERBYA_CHAR)
-----------------------------------------------------------------
a(2),b(1),c(3),d(1),e(2)
If you particularly want to do this in PL/SQL - because you value is already in a PL/SQL variable perhaps - you can do the same thing with a context switch:
set serveroutput on
declare
l_value varchar2(30) := 'aabcccdee';
l_result varchar2(100);
begin
select listagg(a_char || '(' || count(*) || ')', ',') within group (order by a_char)
into l_result
from (
select substr(l_value, level, 1) as a_char
from dual
connect by level <= length(l_value)
)
group by a_char;
dbms_output.put_line(l_result);
end;
/
a(2),b(1),c(3),d(1),e(2)
PL/SQL procedure successfully completed.