id1 a b
4
1 2 3
2 2 3
3 2 4
2 4 4
id2 c d
3
3 3 3
5 2 1
1 3 4
3
SELECT a,b,c
JOIN ON id1=d
SELECT id1,d
JOIN ON a=c
SELECT id2,id1,d
JOIN ON b=c