SQL語句
描述：exhibitiononline表主鍵exhiid， exhibitor表有外鍵 exhid，對應表 exhibitiononline的主鍵exhiid;
exhibitiononline表---------> 一對多 <------------- exhibitor表
功能：查詢出 exhibitiononline表中，exhiid存在於表 exhibitor中的所有數據，並根據 exhibitor表的exhid的數量排序
select * from exhibitiononline join
(select exhid,count(exhid) as s from exhibitor group by exhid) as t
on exhibitiononline.exhiid=t.exhid
order by t.s desc
