写法一：
create table A as
select * from B
;
Create table C as
select a.*,d.*
from D as d
left join A as a on (a.id = d.id)
;
写法二:
Create table C as
select a.*,d.*
from D as d
left join (select * from B) as a
on (a.id = d.id)
;

这两种写法哪种比较快