MySQL 执行顺序

 from
 on
 join
 where
 group by
 having
 select 
 distinct
 order by
 limit

注：where条件的执行顺序，是从左到右

Oracle 执行顺序

from
on
join
where
group by
with
having
select
distinct
order
top

注：where条件的执行顺序，是从右到左