1. Create two tables
Table t1:
| id | name |
| 1 | a1 |
| 3 | a3 |
Table t2:
| id | name |
| 1 | b1 |
| 2 | b2 |
| 5 | b5 |
Joint query merge fields:
| B | c | myId |
|---|---|---|
| a1 | b1 | 1 |
| 0 | b2 | 2 |
| a3 | 0 | 3 |
| 0 | b5 | 5 |
The sql is as follows:
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