demo:
SELECT ROWNUM rn , B.* from B_POINT_COORDINATES B where ROWNUM<=5;
SELECT * from (SELECT ROWNUM rn , B.* from B_POINT_COORDINATES B where ROWNUM<=50) BR WHERE BR.RN>=0 ;
SELECT * from (SELECT ROWNUM rn , B1.* from (SELECT * from B_POINT_COORDINATES B ORDER BY B.SURVEY_POINT DESC ) B1 where ROWNUM<=50) BR WHERE BR.RN>=0 ;
--rownum关键字：oracle对外提供的自动给查询结果编号的关键字，与每行的数据没有关系。
--注意：rownum关键字只能做< <=的判断，不能进行> >=的判断
select rownum ,e.* from emp e;
--查询员工信息的前5条数据 第一页数据
select rownum r,e.* from emp e where rownum <=5;
select * from (select rownum r,e.* from emp e where rownum <=5) t where r>0;
--查询员工信息的6-10条数据 第二页数据
select rownum r,e.* from emp e where rownum <=10;
select rownum,t.* from (select rownum r,e.* from emp e where rownum <=10) t where r>5;
--查询员工信息的11-15条数据 第三页数据
select rownum r,e. * from emp e where rownum<=15;
select * from (select rownum r,e. * from emp e where rownum<=15) t where r>10;
--分页规律总结：每页显示m条数据，查询第n页数据
select * from (select rownum r,e. * from 要分页的表 e where rownum<=m*n) t where r>m*n-m ;
--要分页的表既可以是真实的表，也可以是一个查询语句
--分页查询员工信息按照工资排序
select * from (select rownum r,t.* from (select * from emp order by sal) t where rownum<=10 ) where r>5