Oracle 18c

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CREATE TABLE a AS
SELECT 1 AS a1, 2 AS a2 FROM dual;





1 rows affected

CREATE TABLE b AS
SELECT 1 AS b1 FROM dual;
1 rows affected

CREATE TABLE c AS
SELECT 3 AS c1 FROM dual;
1 rows affected

-- Oracle 12c: code below will work
SELECT * 
FROM a, b, c
WHERE a.a1(+) = b.b1
  AND a.a2(+) = c.c1;


A1
A2
B1
C1


null
null
1
3