CREATE DEFINER=`root`@`localhost` PROCEDURE `getAllpaged`(IN pageSize INT,IN currPage INT)
    DETERMINISTIC
BEGIN
declare Idmax int;
declare lowerbound int;
declare maxpage int;
declare upperbound int;
select max(id) from ftp into Idmax;//选出最大ID
select ceiling(1.0*Idmax/pageSize) into maxPage;//选出最后页的页号
if (currPage>0 and currPage<=maxPage) 
then
select Idmax-pageSize*currPage into lowerbound;
select Idmax-pageSize*(currPage-1) into upperbound;//实现倒选
SELECT * FROM ftp WHERE id>lowerbound AND id<=upperbound order by id desc;
else
set lowerbound=Idmax-pageSize;
SELECT * FROM ftp WHERE id>lowerbound AND id<=Idmax order by id desc;
//若在范围以外则返回第一页
end if;
END