sql效率的比较，请进

trampshi

两个表A和B，A表(id,v1,v2), B表(id,v3,v4),现在要取两表连接的结果集，即(id,v1,v2,v3,v4),以下两个哪个效率高？（假设A，B各有50万条记录）

1。 select A.id,v1,v2,v3,v4 from A outer B where a.id=b.id

2. select id,v1,v2,0 as v3,0 as v4 from A  
    union all
    select id,0,0,v3,v4 from B
    into temp t;
    select id,sum(v1) ,sum(v2),sum(v3),sum(v4) from t;