请问下面两个sql的差别

请教下面两个sql的差别
select   t1.id2,   t1.id3,   t2.name,   t3.name
from   t1,   t2,   t3
where   t1.id2   =   t2.id2   and   t1.id3   =   t3.id3;

select   t1.id2,   t1.id3,
          (select   name   from   t2   where   t1.id2=t2.id2),
          (select   name   from   t3   where   t1.id3=t3.id3)
from   t1;

这两个sql有什么差别，主要是效率上，其余各个方面如果有的话也都要，谢谢

[解决办法]
第一个是一个查询

后一个是三个查询

个人认为是第一个要快些
[解决办法]
看了执行计划
select t1.id2, t1.id3, t2.name, t3.name
from t1, t2, t3
where t1.id2 = t2.id2 and t1.id3 = t3.id3;的效率应该高一些

[解决办法]
第一个比较快，有了子查询，效率都会降低的
[解决办法]
explain一下，什么都明了了
[解决办法]
EXPLAIN EXTENDED select t1.id2, t1.id3, t2.name, t3.name
from t1, t2, t3
where t1.id2 = t2.id2 and t1.id3 = t3.id3;
EXPLAIN EXTENDED select t1.id2, t1.id3,
(select name from t2 where t1.id2=t2.id2),
(select name from t3 where t1.id3=t3.id3)
from t1;