如何产生这样的结果？

Question

sample=# select * from t1;
 f1 | f2
----+----
 x1 | y1
 x2 | y2
(2 rows)

sample=# select * from t2;
 f1 | f3
----+----
 x1 | z1
 x3 | z3
(2 rows)

上面两个数据库的大致结构，我希望产生这样的结果

 f1 | f2 | f3 
----+----+----
 x1 | y1 | z1
 x2 | y2 | 
 x3 |    | z3

如何做到？

Answer 1

FULL JOIN

SELECT (CASE
    WHen t1.f1 IS NULL then t2.f1
    ELSE t1.f1
    end) as f1,
t1.f2,t2.f3 FROM t1 FULL OUTER JOIN t2 on t1.f1=t2.f1