Output as a single row with values separated by comas

Question

I have a query that returns one column as:
Col1
a
b
c
I want the output as a single row with values separated by comas:
Col1
a,b,c
How do I do it in SQL?

Answer 1

Or... build your own aggregation function :
SQL> create or replace type AggregateStr as object
  2  (
  3    tag    VARCHAR2(1),
  4    str    VARCHAR2(4000), -- concatenation string
  5    static function ODCIAggregateInitialize(sctx IN OUT AggregateStr) return number,
  6    member function ODCIAggregateIterate(self IN OUT AggregateStr, value IN VARCHAR2) return number,
  7    member function ODCIAggregateTerminate(self IN AggregateStr, returnValue OUT VARCHAR2, flags IN number) return number,
  8    member function ODCIAggregateMerge(self IN OUT AggregateStr, ctx2 IN AggregateStr) return number
  9  );
10  /
Type created.
Elapsed: 00:00:00.00
SQL>
SQL> create or replace type body AggregateStr is
  2       static function ODCIAggregateInitialize(sctx IN OUT AggregateStr) return number is
  3       begin
  4         sctx := AggregateStr(',','');
  5         return ODCIConst.Success;
  6       end;
  7       
  8       member function ODCIAggregateIterate(self IN OUT AggregateStr, value IN VARCHAR2) return number is
  9       begin
10         self.str:=self.str||value||self.tag;
11         return ODCIConst.Success;
12       end;
13       
14       member function ODCIAggregateTerminate(self IN AggregateStr, returnValue OUT VARCHAR2, flags IN number) return number is
15       begin
16         returnValue := rtrim(self.str,',');
17         return ODCIConst.Success;
18       end;
19       
20       member function ODCIAggregateMerge(self IN OUT AggregateStr, ctx2 IN AggregateStr) return number is
21       begin
22         self.str := ctx2.str;
23         return ODCIConst.Success;
24       end;
25  end;
26  /
Type body created.
Elapsed: 00:00:00.00
SQL>
SQL> CREATE OR REPLACE FUNCTION ConcateStr (input VARCHAR2) RETURN VARCHAR2
  2  PARALLEL_ENABLE AGGREGATE USING AggregateStr;
  3  /
Function created.
Elapsed: 00:00:00.00
SQL>
SQL> select max(concate_string) keep (dense_rank last order by length(concate_string)) as concate_string
  2  from   (select ConcateStr(ename) over (order by ename) concate_string
  3          from   emp);
CONCATE_STRING
ADAMS,ALLEN,BLAKE,CLARK,FORD,JAMES,JONES,KING,MARTIN,MILLER,SCOTT,SMITH,TURNER,WARD
Elapsed: 00:00:00.00Or if you doesn't matter of the order :
SQL> select ConcateStr(ename)
  2  from   emp;
CONCATESTR(ENAME)
SMITH,ALLEN,WARD,JONES,MARTIN,BLAKE,CLARK,SCOTT,KING,TURNER,ADAMS,JAMES,FORD,MILLERNicolas.
adding the second query.
Message was edited by:
N. Gasparotto