请问一个mysql查询有关问题，送上100分

create temporary table A<br />select 1 as uid, 1 as mid, 100 as cash<br />union select 2, 2, 105<br />union select 3, 3,  98<br />union select 4, 4,  55<br />union select 5, 5,  60<br />union select 6, 6,  70;<br /><br />create temporary table B<br />select 1 as uid, 1 as mid, 101 as cash, 100 as  number<br />union select 2,     1,   100,    100<br />union select 3,     2,   105,    200<br />union select 4,     2,   105,    300<br />union select 5,     3,   60,     300<br />union select 6,     3,   98,     300;<br /><br />select uid,mid, cash, (select sum(number) from B where mid=A.mid and cash=A.cash) from A<br />

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