SQL 查询比较

Question

Tables A and B in action.
A [commonfield, otherfields]
B [commonfield]

查询 1

select
        A.otherfields
from
        A,B
where
        A.commonfield = B.commonfield
        and some filters ( A.commonfield )

查询 2

select
        A.otherfields
from
        A
where
        A.commonfield in ( select B.commonfield from B )
        and some filters ( A.commonfield )

查询 1 等同于查询 2。在 (a) 内存使用和 (b) 速度方面哪个更好？

Answer 1

最好的和符合 ANSI 标准的方法是

查询#3:

select
        A.otherfields
from
        A
inner join
        B ON A.commonfield = B.commonfield
where
        some filters ( A.commonfield )