假设A:
id a b
1 10 10
2 20 20
3 30 30
4 40 40
B:
id c d
1 100 100
2 200 200
4 400 400
将A和B左连接(A.id=B.id
id a b c d
1 10 10 100 100
2 20 20 200 200
3 30 30 0 0
4 40 40 400 400
需要类似这样的功能:
select * from A LEFT JOIN B on(A.id=B.id) order by SUM_ALL(A.a+A.b+B.c+B.d)