給定字符串中每個字符的數量

Question

我需要字符串中每個字符的數量。
實施例：

SELECT ('aabcccdee') from dual; 

結果：

a(1),b(2), c(3), d(1),e(2). 

預先感謝。

Answer 1

您可以使用分層查詢將字符串拆分爲單個字符;這是一個使用CTE只是爲了提供您的示例值：

with t (value) as (
    select 'aabcccdee' from dual 
) 
select substr(value, level, 1) as a_char 
from t 
connect by level <= length(value); 

然後你可以使用聚合計算會如何次，每次出現：

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 

你也可以使用listagg()（如果你是11g或以上）聚合這些字符計數成一個字符串，如果這是你真正想要的：

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) 

如果你特別想這樣做，在PL/SQL - 因爲你重視我s已經在PL/SQL變量中 - 也許你可以用上下文開關做同樣的事情：

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.