mysql 全连接查询合并字段

1、创建两张表

表t1:

id	name
1	a1
3	a3

表t2: 

id	name
1	b1
2	b2
5	b5

联合查询合并字段： 

B	c	myId
a1	b1	1
0	b2	2
a3	0	3
0	b5	5

sql如下：

SELECT IFNULL(t3.name,0) as B, IFNULL(t3.name1,0) as C , COALESCE(t3.id2,t3.id1) as myId FROM ( SELECT t1.id as id2 ,t1.`name` as name,t2.id as id1 ,t2.`name` as name1 FROM t1 LEFT JOIN t2 on t1.id=t2.id

UNION

SELECT t1.id as id2 ,t1.`name` as name,t2.id as id1 ,t2.`name` as name1 FROM t1 RIGHT JOIN t2 on t1.id=t2.id ) as t3 GROUP BY myId