撤消紅移

Question

一個LISTAGG我有一個表，可能是由於一個LISTAGG，與此類似：

# select * from s; 
    s  
----------- 
a,c,b,d,a 
b,e,c,d,f 
(2 rows) 

我怎樣才能把它變成該行集：

a 
c 
b 
d 
a 
b 
e 
c 
d 
f 

Answer 1

在紅移，你可以加入對數表，並用它作爲分割指數：

with recursive Numbers as (
    select 1 as i 
    union all 
    select i + 1 as i from Numbers where i <= 5 
) 
select split_part(s,',', i) from Numbers, s ORDER by s,i; 

編輯：redshift似乎不支持遞歸子查詢，只有postgres。 :(

Answer 2

SQL Fiddle

的Oracle 11g R2架構設置：

create table s(
    col varchar2(20)); 

insert into s values('a,c,b,d,a'); 
insert into s values('b,e,c,d,f'); 

查詢1：

SELECT REGEXP_SUBSTR(t1.col, '([^,])+', 1, t2.COLUMN_VALUE) 
FROM s t1 CROSS JOIN 
TABLE 
(
    CAST 
    (
    MULTISET 
    (
     SELECT LEVEL 
     FROM DUAL 
     CONNECT BY LEVEL <= REGEXP_COUNT(t1.col, '([^,])+') 
    ) 
    AS SYS.odciNumberList 
) 
) t2 

Results：

| REGEXP_SUBSTR(T1.COL,'([^,])+',1,T2.COLUMN_VALUE) | 
|---------------------------------------------------| 
|             a | 
|             c | 
|             b | 
|             d | 
|             a | 
|             b | 
|             e | 
|             c | 
|             d | 
|             f |