Oracle 18c

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CREATE TABLE TEST01(A VARCHAR2(10),B VARCHAR2(40),QTY number(10));
INSERT INTO TEST01(A,B,QTY) VALUES('A1','B1',10);
1 rows affected

INSERT INTO TEST01(A,B,QTY) VALUES('A1','B2',20);
1 rows affected

INSERT INTO TEST01(A,B,QTY) VALUES('A1','B1',30);
1 rows affected

INSERT INTO TEST01(A,B,QTY) VALUES('A2','B2',40);
1 rows affected

INSERT INTO TEST01(A,B,QTY) VALUES('A2','B3',10);
1 rows affected

SELECT *
FROM TEST01 ;


A
B
QTY


A1
B1
10

A1
B2
20

A1
B1
30

A2
B2
40

A2
B3
10


SELECT 
CASE WHEN AORDER=1 THEN A ELSE '' END AS A,B,QTY1 AS QTY,
A AS ATEMP,AORDER
FROM (
SELECT A,B,SUM(QTY) AS QTY1,
ROW_NUMBER() OVER(PARTITION BY A ORDER BY A,B) AS AORDER
FROM TEST01 
WHERE 1=1
GROUP BY A,B
) "TEMP1"
WHERE 1=1
--
UNION
SELECT A,'' AS B,SUM(QTY) AS QTY1,
A AS ATEMP,COUNT(1)+1 AORDER
FROM TEST01 
WHERE 1=1
GROUP BY A
ORDER BY ATEMP,AORDER,B


A
B
QTY
ATEMP
AORDER


A1
B1
40
A1
1

null
B2
20
A1
2

A1
null
60
A1
4

A2
B2
40
A2
1

null
B3
10
A2
2

A2
null
50
A2
3

A	B	QTY	ATEMP	AORDER
A1	B1	40	A1	1
null	B2	20	A1	2
A1	null	60	A1	4
A2	B2	40	A2	1
null	B3	10	A2	2
A2	null	50	A2	3