MySQL 8.0

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create table tblProduct (id integer);
create table tblProductSales (id integer);
INSERT INTO tblProduct VALUES (1),(2),(3),(8),(9),(9);

INSERT INTO tblProductSales VALUES (1),(1),(2),(3),(4),(5);


SELECT * FROM tblProduct P
LEFT JOIN tblProductSales S ON P.id = S.id
UNION ALL
SELECT * FROM tblProduct P
RIGHT JOIN tblProductSales S ON P.id = S.id
WHERE P.id IS NULL


id
id


1
1

1
1

2
2

3
3

8
null

9
null

9
null

null
4

null
5

id	id
1	1
1	1
2	2
3	3
8	null
9	null
9	null
null	4
null	5