How to get all substring occurences between some characters? - sql

Question

What i'm trying to get is the part of a column text that is between some characters ($$ to be exact) but the trick is those characters can occur more than twice (but always even like if there are more than 2 than it must be like $$xxx$$ ... $$yyy$$) and I need to get them separately.
When I try this, if the pattern only occur once then it's no problem :
regexp_substr(txt,'\$\$(.*)\$\$',1,1,null,1)
But lets say the column text is : $$xxx$$ ... $$yyy$$
then it gives me : xxx$$ ... $$yyy
but what I need is two get them in separate lines like :
xxx
yyy
which I couldn't get it done so how?

Answer 1

You could use a recursive query that matches the first occurrence and then removes that from the string for the next iteration of the recursive query.
Assuming your table and column are called tbl and txt:
with cte(match, txt) as (
select regexp_substr(txt,'\$\$(.*?)\$\$', 1, 1, null, 1),
regexp_replace(txt,'\$\$(.*?)\$\$', '', 1, 1)
from tbl
where regexp_like(txt,'\$\$(.*?)\$\$')
union all
select regexp_substr(txt,'\$\$(.*?)\$\$', 1, 1, null, 1),
regexp_replace(txt,'\$\$(.*?)\$\$', '', 1, 1)
from cte
where regexp_like(txt,'\$\$(.*?)\$\$')
)
select match from cte

Answer 2

One could also use CONNECT BY to "loop" through the elements surrounded by the double dollar signs, returning the data inside (the 2nd grouping). This method handles NULL elements (ID 7, element 2) and since the dollar signs are consumed as the regex moves from left to right, characters in between the groups are not falsely matched.
SQL> with tbl(id, txt) as (
select 1, '$$xxx$$' from dual union all
select 2, '$$xxx$$ ... $$yyy$$' from dual union all
select 3, '' from dual union all
select 4, '$$xxx$$abc$$yyy$$' from dual union all
select 5, '$$xxx$$ ... $$yyy$$ ... $$www$$ ... $$zzz$$' from dual union all
select 6, '$$aaa$$$$bbb$$$$ccc$$$$ddd$$' from dual union all
select 7, '$$aaa$$$$$$$$ccc$$$$ddd$$' from dual
)
select id, level, regexp_substr(txt,'(\$\$(.*?)\$\$)',1,level,null,2) element
from tbl
connect by regexp_substr(txt,'(\$\$(.*?)\$\$)',1,level) is not null
and prior txt = txt
and prior sys_guid() is not null
order by id, level;
ID LEVEL ELEMENT
---------- ---------- -------------------------------------------
1 1 xxx
2 1 xxx
2 2 yyy
3 1
4 1 xxx
4 2 yyy
5 1 xxx
5 2 yyy
5 3 www
5 4 zzz
6 1 aaa
6 2 bbb
6 3 ccc
6 4 ddd
7 1 aaa
7 2
7 3 ccc
7 4 ddd
18 rows selected.
SQL>