如何在mysql中完成两个表的全外连接？

Question

我有两个表payroll_advance和payroll_advrtn，我应该做完整的外部联接以获得我的要求结果。但是，我确信完整的外部联接在mysql中是不可能的，而且我知道完全外部连接是可能的通过使用union.But我不知道我怎么能加入在下面的查询。

我的payroll_advance表产生以下结果。

SELECT _id,_tid,_dt,sum(_amount) as _advance FROM payroll_advance WHERE YEAR(_dt)=YEAR(CURDATE()) AND MONTH(_dt) = MONTH(CURDATE()) group by _tid; 

+-----+-------+------------+---------+ 
| _id | _tid | _dt  | _advance| 
+-----+-------+------------+---------+ 
| 17 | hjg | 2012-04-18 | 2151 | 
| 22 | RKT01 | 2012-04-10 | 2098 | 
| 14 | RKT04 | 2012-04-18 | 1511 | 
| 16 | RKT09 | 2012-04-09 |  250 | 
| 15 | RKT10 | 2012-04-17 | 1313 | 
| 8 | RKT21 | 2012-04-03 | 1321 | 
| 19 | RKT31 | 2012-04-26 | 2512 | 
| 20 | RKT33 | 2012-04-10 | 2250 | 
| 25 | T01 | 2012-04-11 | 2500 | 
+-----+-------+------------+---------+ 

并且payroll_advrtn给出以下结果。

SELECT _id,_tid,_dt,sum(_amount) as _advrtn FROM payroll_advrtn WHERE YEAR(_dt) = YEAR(CURDATE()) AND MONTH(_dt) = MONTH(CURDATE()) group by _tid; 
+-----+-------+------------+---------+ 
| _id | _tid | _dt  | _advrtn | 
+-----+-------+------------+---------+ 
| 9 | RKT02 | 2012-04-10 | 2500 | 
| 8 | RKT04 | 2012-04-20 |  150 | 
+-----+-------+------------+---------+ 

但我想通过结合上述两个结果像下面的结果。

+------+-------+-------+------------+----------+---------+ 
| _id | _tid | _tid | _dt  | _advance | _advrtn | 
+------+-------+-------+------------+----------+---------+ 
| 17 | hjg | NULL | 2012-04-18 |  2151 | NULL | 
| 22 | RKT01 | NULL | 2012-04-10 |  999 | NULL | 
| 14 | RKT04 | RKT04 | 2012-04-18 |  11 |  150 | 
| 16 | RKT09 | NULL | 2012-04-09 |  250 | NULL | 
| 15 | RKT10 | NULL | 2012-04-17 |  1313 | NULL | 
| 8 | RKT21 | NULL | 2012-04-03 |  1321 | NULL | 
| 19 | RKT31 | NULL | 2012-04-26 |  2512 | NULL | 
| 20 | RKT33 | NULL | 2012-04-10 |  2250 | NULL | 
| 25 | T01 | NULL | 2012-04-11 |  2500 | NULL | 
| NULL | NULL | RKT02 | NULL  |  NULL | 2500 | 
+------+-------+-------+------------+----------+---------+ 

任何帮助将不胜感激。谢谢！

Answer 1

为了做FULL OUTER JOINyou can do的LEFT OUTER JOIN和UNION与RIGHT OUTER JOIN（ 提供 MySql依然不支持 FULL OUTER JOIN ）：

select * from A as a 
    left outer join B as b on a.col = b.col 
union 
select * from A as a 
    right outer join B as b on a.col = b.col 

注意，您可以使用子查询为A和B - 这应该与您的查询一起工作。你的情况：

select * from (SELECT * FROM t1) as a 
    left outer join (SELECT * FROM t2) as b on a._tid = b._tid 
union 
select * from (SELECT * FROM t1) as a 
    right outer join (SELECT * FROM t2) as b on a._tid = b._tid 

有了结果等于（前提是我没有我在复制粘贴你的数据有误）：

+------+-------+------------+----------+------+-------+------------+----------+ 
| _id | _tid | _dt  | _advance | _id | _tid | _dt  | _advartn | 
+------+-------+------------+----------+------+-------+------------+----------+ 
| 17 | hjg | 2012-04-18 |  2151 | NULL | NULL | NULL  |  NULL | 
| 22 | RKT01 | 2012-04-10 |  2098 | NULL | NULL | NULL  |  NULL | 
| 14 | RKT04 | 2012-04-18 |  1511 | 8 | RKT04 | 2012-04-20 |  150 | 
| 16 | RKT09 | 2012-04-09 |  250 | NULL | NULL | NULL  |  NULL | 
| 15 | RKT10 | 2012-04-17 |  1313 | NULL | NULL | NULL  |  NULL | 
| 8 | RKT21 | 2012-04-03 |  1321 | NULL | NULL | NULL  |  NULL | 
| 19 | RKT31 | 2012-04-26 |  2512 | NULL | NULL | NULL  |  NULL | 
| 20 | RKT33 | 2012-04-10 |  2250 | NULL | NULL | NULL  |  NULL | 
| 25 | T01 | 2012-04-11 |  2500 | NULL | NULL | NULL  |  NULL | 
| NULL | NULL | NULL  |  NULL | 9 | RKT02 | 2012-04-10 |  2500 | 
+------+-------+------------+----------+------+-------+------------+----------+ 

Answer 2

商店这样既查询的结果：

create temporary table a as select ... ; 
create temporary table b as select ... ; 

然后：

select * from a left join b using (_tid) 
union 
select * from a right join b using (_tid);