Select statement with a dynamic group by clause - oracle

Question

How possible to group records conditionally? For example I have records with FLOW_NUMBER column, values 1, 2, 3. When FLOW_NUMBER value is 1, I want to group this records, but when FLOW_NUMBER is 2 or 3, I don't want to group.
SELECT
LISTAGG(DISTINCT PRODORD, ',') PRODORD,
SUM(QTY) AS QTY
FROM (
SELECT
1 AS FLOW_NUMBER,
'A' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
1 AS FLOW_NUMBER,
'B' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
1 AS FLOW_NUMBER,
'C' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
2 AS FLOW_NUMBER,
'A' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
2 AS FLOW_NUMBER,
'B' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
2 AS FLOW_NUMBER,
'C' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
3 AS FLOW_NUMBER,
'A' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
3 AS FLOW_NUMBER,
'B' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
3 AS FLOW_NUMBER,
'C' AS PRODORD,
1 AS QTY
FROM DUAL
)
GROUP BY FLOW_NUMBER -- bad group by clause
There is example photo of group by which I need.

Answer 1

SELECT SUBSTR(flow,1,INSTR(flow,'/')-1) AS flow, LISTAGG(prodorder,',') WITHIN GROUP(ORDER BY prodorder) AS prodorders, SUM(qty) AS qty
FROM (
SELECT CASE WHEN flow=1 THEN '1/' ELSE to_CHAR(flow)||'/'||ROWNUM END AS flow,
prodorder, qty FROM DATA
)
GROUP BY flow;

Answer 2

I don't think there is anyway to achieve it except using 2 query combined with UNION ALL clause -
SELECT FLOW_NUMBER, LISTAGG(DISTINCT PRODORD, ',') PRODORD,
SUM(QTY) AS QTY
FROM temp
WHERE FLOW_NUMBER = 1
GROUP BY FLOW_NUMBER
UNION ALL
SELECT FLOW_NUMBER, PRODORD,
QTY
FROM temp
WHERE FLOW_NUMBER <> 1;
Demo.

Answer 3

You can try this:
select
substr(fn,1,decode(instr(fn,','),0,1000,instr(fn,','))-1) flow_number,
prodord, qty
from (SELECT
case when FLOW_NUMBER=1 then to_char(flow_number) else to_char(flow_number)||','||rownum end fn,
LISTAGG(DISTINCT PRODORD, ',') PRODORD,
SUM(QTY) AS QTY
FROM (
SELECT
1 AS FLOW_NUMBER,
'A' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
1 AS FLOW_NUMBER,
'B' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
1 AS FLOW_NUMBER,
'C' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
2 AS FLOW_NUMBER,
'A' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
2 AS FLOW_NUMBER,
'B' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
2 AS FLOW_NUMBER,
'C' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
3 AS FLOW_NUMBER,
'A' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
3 AS FLOW_NUMBER,
'B' AS PRODORD,
1 AS QTY
FROM DUAL
UNION ALL
SELECT
3 AS FLOW_NUMBER,
'C' AS PRODORD,
1 AS QTY
FROM DUAL
)
GROUP BY case when FLOW_NUMBER=1 then to_char(flow_number) else to_char(flow_number)||','||rownum end);
I used rownum here, but you can probably replace it by other things (e.g. rowid, if the data is from a table, just be sure to have a unique value)