Oracle分页SQL

 错误写法：

select a.*, rownum r
from (select * from lg_order o order by o.order_id) a
where rownum <= 20
   and rownum >= 10

正确写法：

select *
from (select a.*, rownum r
          from (select * from lg_order o order by o.order_id) a
         where rownum <= 20) b
where r >= 10

第一句是错误的 由于rownum是一个总是从1开始的伪列，Oracle 认为这种条件不成立，查不到记录
执行顺序从内到外，从右到左