请问一个mysql查询有关问题，送上100分

create temporary table A

select 1 as uid, 1 as mid, 100 as cash

union select 2, 2, 105

union select 3, 3,  98

union select 4, 4,  55

union select 5, 5,  60

union select 6, 6,  70;



create temporary table B

select 1 as uid, 1 as mid, 101 as cash, 100 as  number

union select 2,     1,   100,    100

union select 3,     2,   105,    200

union select 4,     2,   105,    300

union select 5,     3,   60,     300

union select 6,     3,   98,     300;



select uid,mid, cash, (select sum(number) from B where mid=A.mid and cash=A.cash) from A

select a.uid, a.mid, a.cash, sum(b.number) from testa as a left join testb as b on a.mid=b.mid and a.cash = b.cash group by a.mid, a.cash