CREATE TABLE T1(A VARCHAR2(10),B VARCHAR2(10),C VARCHAR2(2));
CREATE TABLE T2(A VARCHAR2(10),B VARCHAR2(10),D VARCHAR2(2));
INSERT INTO T1 VALUES(111,222,1);
INSERT INTO T1 VALUES(111,333,1);
INSERT INTO T2 VALUES(111,222,2);
INSERT INTO T2 VALUES(111,444,2);
SELECT * FROM T1;
SELECT * FROM T2;

SELECT NVL(T1.A,T2.A) A,
       NVL(T1.B,T2.B) B,
       C,
       D 
FROM T1 FULL JOIN T2 
     ON T1.A=T2.A AND T1.B=T2.B;
结果为：
A          B          C  D  
---------- ---------- -- -- 
111        222        1  2  
111        333        1     
111        444           2

------解决方案--------------------
SQL code

with t1 as(
select '111' a,'222' b,'1' c from dual
union all
select '111' a,'333' b,'1' c from dual
),
t2 as(
select '111' a,'222' b,'2' d from dual
union all
select '111' a,'444' b,'2' d from dual
)

select t1.a, t1.b, t1.c,t2.d
  from t1, t2
 where t1.a = t2.a
   and t1.b = t2.b
   
   union 

select t1.a, t1.b, t1.c,t2.d
  from t1, t2
 where t1.a = t2.a(+)
   and t1.b = t2.b(+)

   union 

select t2.a, t2.b, t1.c,t2.d
  from t1, t2
 where t1.a(+) = t2.a
   and t1.b(+) = t2.b

------解决方案--------------------

左连接和右连接的并集
SQL code
WITH t1 AS(
SELECT 111 ca,222 cb,1 cc FROM dual
UNION ALL 
SELECT 111,333,1 FROM dual
),t2 AS (
SELECT 111 ca,222 cb,2 cd FROM dual
UNION ALL            
SELECT 111,444,2 FROM dual
)
SELECT t1.ca,t1.cb,t1.cc,t2.cd FROM t1 left join t2 ON t1.ca=t2.ca AND t1.cb=t2.cb
UNION 
SELECT t2.ca,t2.cb,t1.cc,t2.cd FROM t1 right join t2 ON t1.ca=t2.ca AND t1.cb=t2.cb

------解决方案--------------------
精彩
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SQL code
CREATE TABLE T1(A VARCHAR2(10),B VARCHAR2(10),C VARCHAR2(2));
CREATE TABLE T2(A VARCHAR2(10),B VARCHAR2(10),D VARCHAR2(2));
INSERT INTO T1 VALUES(111,222,1);
INSERT INTO T1 VALUES(111,333……