PostgreSQL FULL JOIN 多表联合查询

只要其中某个表存在匹配，full join 关键字就会返回行。

FULL JOIN 关键字语法
SELECT column_name(s)
FROM table_name1
FULL JOIN table_name2
ON table_name1.column_name=table_name2.column_name
注释：在某些中， FULL JOIN 称为 FULL OUTER JOIN。

postgres=# postgres=# CREATE TABLE t1 ( postgres(#     num         int, postgres(#     name       varchar(10) postgres(# ); CREATE TABLE postgres=# postgres=# insert into t1 values(1,'a'); INSERT 0 1 postgres=# insert into t1 values(2,'b'); INSERT 0 1 postgres=# insert into t1 values(3,'c'); INSERT 0 1 postgres=# postgres=# CREATE TABLE t2 ( postgres(#     num         int, postgres(#     name       varchar(10) postgres(# ); CREATE TABLE postgres=# postgres=# insert into t2 values(1,'xxx'); INSERT 0 1 postgres=# insert into t2 values(3,'yyy'); INSERT 0 1 postgres=# insert into t2 values(5,'zzz'); INSERT 0 1 postgres=# postgres=# SELECT * FROM t1 FULL JOIN t2 ON t1.num = t2.num;  num | name | num | name -----+------+-----+------    1 | a    |   1 | xxx    2 | b    |     |    3 | c    |   3 | yyy      |      |   5 | zzz