1、常用分页： 只有通过伪列ROWNUM来实现 越到后面记录查询越慢！对于千万数据很慢！
SELECT *
FROM (SELECT T.*, ROWNUM AS R
FROM (SELECT * FROM TABLENAME) T
WHERE ROWNUM <= 10)
WHERE R >= 1
2、高效分页：
SELECT *
FROM (SELECT T.*, ROW_NUMBER() OVER(ORDER BY N_COUNT DESC) R
FROM T_NEWS T) T
WHERE R BETWEEN 4 AND 6
--通用语法： 解析函数() over(partition by 字段 order by 字段)
-- partition by 分组
-- order by 排序