MySQL全连接(Full Join）实现

[size=medium]MYSQL 可以用 union 实现全连接
mysql> select * from a;
+------+
| id |
+------+
| 1 |
| 2 |
| 3 |
+------+
3 rows in set (0.00 sec)

mysql> select * from b;
+------+
| id |
+------+
| 1 |
| 2 |
| 4 |
+------+
3 rows in set (0.00 sec)

mysql> select a.id,b.id from a left join b on a.id=b.id union select a.id,b.id f
rom a right join b on a.id=b.id;
+------+------+
| id | id |
+------+------+
| 1 | 1 |
| 2 | 2 |
| 3 | NULL |
| NULL | 4 |
+------+------+
4 rows in set (0.00 sec)

mysql>[/size]