Aggregation Function

Question

I followed an example on the web and created a LIST() aggregation function to transpose rows to a comma delimited string. After certain length, the result appears to be out of order. I thought it was parallel_enable issue, but it's the same after I removed the clause from CREATE FUNCTION statement.
For example, the following SQL
SELECT LIST(column_name) FROM user_tab_columns
WHERE table_name='TEST' ORDER BY column_id
generate the following string:
c122,c123,c124,...,c1,c2,c3,...,c121
What should I do to correct this behavior? Thanks.
Here is the script:
create or replace type ListType as object
(list varchar2(4000),
static function ODCIAggregateInitialize(sctx IN OUT ListType) return number,
member function ODCIAggregateIterate(self IN OUT ListType, value IN varchar2) return number,
member function ODCIAggregateTerminate(self IN ListType, returnValue OUT varchar2, flags IN number) return number,
member function ODCIAggregateMerge(self IN OUT ListType, ctx2 IN ListType) return number
create or replace type body ListType
is
static function ODCIAggregateInitialize(sctx IN OUT ListType)
return number is
begin
sctx := ListType(null);
return ODCIConst.Success;
end;
member function ODCIAggregateIterate(self IN OUT ListType, value IN varchar2)
return number is
begin
self.list := self.list || ',' || value;
return ODCIConst.Success;
end;
member function ODCIAggregateTerminate(self IN ListType, returnValue OUT varchar2, flags IN number)
return number is
begin
returnValue := rtrim(ltrim(self.list,','),',');
return ODCIConst.Success;
end;
member function ODCIAggregateMerge(self IN OUT ListType, ctx2 IN ListType)
return number is
begin
self.list := self.list|| ',' || ctx2.list;
return ODCIConst.Success;
end;
end;
create or replace function list(input varchar2) return varchar2
parallel_enable aggregate using ListType;
grant EXECUTE on list to PUBLIC
/

Answer 1

in 10g, you could use something like
regexp_replace( list(distinct to_char(column_id,'0000')||':'||column_name), '([:[digit]:]){4}:')
if you need to support 9i, you cannot use regular expression, but you can write your own function and concatenated substr. kind of loop with instr(:) and substr()
HTH
Laurent
Message was edited by:
Laurent Schneider
but, if you need to sort, use ORDER BY. my solution is a not recommended, it is a very dirty trick
Message was edited by:
Laurent Schneider
use order by within your aggregate function, to sort the resultset each time, as advised by tom kyte in the link above